:original_name: en-us_topic_0054235814.html

.. _en-us_topic_0054235814:

Configuring Redis-Specific Parameters
=====================================

On the DCS console, you can configure Redis-specific parameters to keep DCS instances performing optimally.

.. note::

   The default values are already optimized for typical use cases. Reconfiguring parameters is recommended only when necessary.

Prerequisites
-------------

The DCS instance you want to configure is in the **Running** state, and the instance type is single-node or master/standby (Redis parameters of DCS instances in Proxy Cluster mode are not modifiable).

Procedure
---------

#. Log in to the management console.

#. Click |image1| in the upper left corner of the management console and select a region.

#. Click **Service List**, and choose **Database** > **Distributed Cache Service** to launch the DCS console.

#. In the navigation pane, choose **Cache Manager**.

#. On the **Cache Manager** page, click the name of the DCS instance you want to configure.

   A page with details of the DCS instance is displayed.

#. On the instance details page, click the **Parameters** tab.

#. On the **Parameters** tab page, click **Modify**.

#. Modify Redis-specific parameters based on your requirements.

   .. note::

      The Redis parameters supported by single-node and master/standby instances are different. The following parameters are only supported by master/standby instances, but are not supported by single-node instances:

      -  appendfsync
      -  appendonly
      -  repl-backlog-size
      -  repl-backlog-ttl

   .. table:: **Table 1** Redis-specific parameters

      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | Parameter                 | Description                                                                                                                                                                                                                                                                             | Value Range                                                                                                                                                                                         | Default Value   |
      +===========================+=========================================================================================================================================================================================================================================================================================+=====================================================================================================================================================================================================+=================+
      | appendfsync               | Controls how often fsync() transfers cached data to the disk. Note that some OSs will perform a complete data transfer but some others only make a "best-effort" attempt.                                                                                                               | -  no                                                                                                                                                                                               | everysec        |
      |                           |                                                                                                                                                                                                                                                                                         | -  always                                                                                                                                                                                           |                 |
      |                           | There are three settings:                                                                                                                                                                                                                                                               | -  everysec                                                                                                                                                                                         |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | **no**: fsync() is never called. The OS will flush data when it is ready. This mode offers the highest performance.                                                                                                                                                                     |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | **always**: fsync() is called after every write to the AOF. This mode is very slow, but also very safe.                                                                                                                                                                                 |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | **everysec**: fsync() is called once per second. This mode provides a compromise between safety and performance.                                                                                                                                                                        |                                                                                                                                                                                                     |                 |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | repl-backlog-size         | The replication backlog size (bytes). The backlog is a buffer that accumulates replica data when replicas are disconnected from the master. When a replica reconnects, a partial synchronization is performed to synchronize the data that was missed while replicas were disconnected. | 16,384-1,073,741,824                                                                                                                                                                                | 1,048,576       |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | repl-backlog-ttl          | The amount of time, in seconds, before the backlog buffer is released, starting from the last a replica was disconnected. The value **0** indicates that the backlog is never released.                                                                                                 | 0-604,800                                                                                                                                                                                           | 3,600           |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | appendonly                | Indicates whether to log each modification of the instance. By default, data is written to disks asynchronously in Redis. If this function is disabled, recently-generated data might be lost in the event of a power failure. Options:                                                 | -  yes                                                                                                                                                                                              | yes             |
      |                           |                                                                                                                                                                                                                                                                                         | -  no                                                                                                                                                                                               |                 |
      |                           | **yes**: enabled                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | **no**: disabled                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                     |                 |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | maxmemory-policy          | How DCS will select what to remove when maxmemory is reached.                                                                                                                                                                                                                           | volatile-lru                                                                                                                                                                                        | noeviction      |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | For more information about this parameter, see :ref:`What Is the Default Data Eviction Policy? <en-us_topic_0054235830>`.                                                                                                                                                               | allkeys-lru                                                                                                                                                                                         |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | volatile-random                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | allkeys-random                                                                                                                                                                                      |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | volatile-ttl                                                                                                                                                                                        |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | noeviction                                                                                                                                                                                          |                 |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | hash-max-ziplist-entries  | When the number of entries in hashes is less than the value of this parameter, hashes are encoded using a memory efficient data structure.                                                                                                                                              | 1 to 10000                                                                                                                                                                                          | 512             |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | hash-max-ziplist-value    | When the biggest entry in hashes does not exceed the length threshold indicated by this parameter, hashes are encoded using a memory efficient data structure.                                                                                                                          | 1 to 10000                                                                                                                                                                                          | 64              |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | list-max-ziplist-entries  | When the number of entries in lists is less than the value of this parameter, lists are encoded using a memory efficient data structure.                                                                                                                                                | 1 to 10000                                                                                                                                                                                          | 512             |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | list-max-ziplist-value    | When the biggest entry in lists does not exceed the length threshold indicated by this parameter, lists are encoded using a memory efficient data structure.                                                                                                                            | 1 to 10000                                                                                                                                                                                          | 64              |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | set-max-intset-entries    | When a set is composed entirely of strings that happen to be integers in radix 10 in the range of 64 bit signed integers, sets are encoded using a memory efficient data structure.                                                                                                     | 1 to 10000                                                                                                                                                                                          | 512             |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | zset-max-ziplist-entries  | When the number of entries in sorted sets is less than the value of this parameter, sorted sets are encoded using a memory efficient data structure.                                                                                                                                    | 1 to 10000                                                                                                                                                                                          | 128             |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | zset-max-ziplist-value    | When the biggest entry in sorted sets does not exceed the length threshold indicated by this parameter, sorted sets are encoded using a memory efficient data structure.                                                                                                                | 1 to 10000                                                                                                                                                                                          | 64              |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | latency-monitor-threshold | Only events that run in more time than the configured latency-monitor-threshold will be logged as latency spikes.                                                                                                                                                                       | 0 to 86,400,000 ms                                                                                                                                                                                  | 0               |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | -  If the latency-monitor-threshold is set to 0, latency monitoring is disabled.                                                                                                                                                                                                        |                                                                                                                                                                                                     |                 |
      |                           | -  If the latency-monitor-threshold is set to a value greater than 0, all events blocking the server for a time equal to or greater than the configured latency-monitor-threshold will be logged.                                                                                       |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | By running the LATENCY command, you can perform operations related to latency monitoring, such as enabling latency monitoring, reporting the latest latency events logged, and obtaining statistical data.                                                                              |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           | For more information about the latency-monitor-threshold, visit https://redis.io/docs/reference/optimization/latency-monitor/.                                                                                                                                                          |                                                                                                                                                                                                     |                 |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | reserved-memory-percent   | Percentage of the maximum available memory reserved for background processes, such as data persistence and replication.                                                                                                                                                                 | 0-80                                                                                                                                                                                                | 0               |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | timeout                   | Connection between the client and server (DCS instance) will be closed if the client is idle for the timeout period (measured in seconds). A timeout period of 0 seconds indicates that the timeout function is disabled.                                                               | 0 to 7200 seconds                                                                                                                                                                                   | 0               |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | notify-keyspace-events    | Keyspace event notification. If this parameter is configured, the Redis Sub/Pub feature will allow clients to receive an event when a Redis data set is modified.                                                                                                                       | If the parameter value is an empty character string, keyspace event notification is disabled.                                                                                                       | ""              |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | If the parameter value is a string of multiple characters, keyspace event notification is enabled and each character identifies a class of keyspace events for which Redis will send notifications. |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | .. note::                                                                                                                                                                                           |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |    -  The parameter value must contain either K or E.                                                                                                                                               |                 |
      |                           |                                                                                                                                                                                                                                                                                         |    -  A is an alias for "g$lshzxe"and cannot be used together with any of the characters "g$lshzxe".                                                                                                |                 |
      |                           |                                                                                                                                                                                                                                                                                         |    -  For example, the value Kl means that Redis will notify Pub/Sub clients about keyspace events and list commands. The value AKE means Redis will notify Pub/Sub clients about all events.       |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | K: Keyspace events, published with the \__keyspace@_\_ prefix                                                                                                                                       |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | E: Keyevent events, published with \__keyevent@_\_ prefix                                                                                                                                           |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | g: Generic commands (non-type specific) such as DEL, EXPIRE, and RENAME                                                                                                                             |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | $: String commands                                                                                                                                                                                  |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | l: List commands                                                                                                                                                                                    |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | s: Set commands                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | h: Hash commands                                                                                                                                                                                    |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | z: Sorted set commands                                                                                                                                                                              |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | x: Expired events (events generated every time a key expires)                                                                                                                                       |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | e: Evicted events (events generated when a key is evicted for maxmemory)                                                                                                                            |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | A: Alias for "g$lshzxe", so that the "AKE" string means all the events.                                                                                                                             |                 |
      |                           |                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                     |                 |
      |                           |                                                                                                                                                                                                                                                                                         | Note that the parameter value must contain either K or E.                                                                                                                                           |                 |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | slowlog-log-slower-than   | The maximum amount of time allowed, in microseconds, for command execution. If this threshold is exceeded, Redis Slow Log will record the command.                                                                                                                                      | 0-1,000,000                                                                                                                                                                                         | 10,000          |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+
      | slowlog-max-len           | The maximum allowed length of the Redis Slow Log logs. Slow Log consumes memory, but you can reclaim this memory by running the SLOWLOG RESET command.                                                                                                                                  | 0-1,000                                                                                                                                                                                             | 128             |
      +---------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+

   .. note::

      -  For more information about Redis-specific parameters, visit https://redis.io/topics/memory-optimization.
      -  The latency-monitor-threshold parameter is usually used for fault location. After locating faults based on the latency information collected, change the value of **latency-monitor-threshold** to **0** to avoid unnecessary latency.

#. After you have finished setting parameters, click **Save**.

#. Click **Yes** to confirm.

.. |image1| image:: /_static/images/en-us_image_0000001340285305.png