Synchronize a single index.

The request URL and request body parameters are as follows:

PUT start_remote_sync

**Table 1** Request body parameters
Parameter	Description
remote_cluster	Name of the primary cluster. The default name is leader1. You can change the name by configuring the primary cluster information.
remote_index	Name of the index to be synchronized in the primary cluster
local_index	Name of the index being synchronized to the secondary cluster
settings	Index settings of the index being synchronized

After the synchronization function is enabled, indexes in the secondary cluster become read-only and are periodically synchronized with indexes in the primary cluster.

The following are two examples:

Synchronize a single index from the primary cluster to the secondary cluster.

PUT start_remote_sync
{
  "remote_cluster": "leader1",
  "remote_index": "data1_leader",
  "local_index": "data1_follower"
}

Synchronize a single index from the primary cluster to the secondary cluster and modify the index configurations.
```
PUT start_remote_sync
{
  "remote_cluster": "leader1",
  "remote_index": "data1_leader",
  "local_index": "data1_follower",
  "settings": {
    "number_of_replicas": 4
  }
}
```
The following index configurations cannot be modified:
- number_of_shards
- version.created
- uuid
- creation_date
- soft_deletes.enabled

Synchronizing Specified Indexes