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Elastic Docs ›Elasticsearch Guide [7.9] ›ILM: Manage the index lifecycle ›Index lifecycle actions
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Force mergeedit

Phases allowed: hot, warm.

Force merges the index into the specified maximum number of segments.

This action makes the index read-only.

To use the forcemerge action in the hot phase, the rollover action must be present. If no rollover action is configured, ILM will reject the policy.

Optionsedit

max_num_segments
(Required, integer) Number of segments to merge to. To fully merge the index, set to 1.
index_codec

(Optional, string) Codec used to compress the document store. The only accepted value is best_compression, which uses DEFLATE for a higher compression ratio but slower stored fields performance. To use the default LZ4 codec, omit this argument.

If using best_compression, ILM will close and then re-open the index prior to the force merge. While closed, the index will be unavailable for read or write operations.

Exampleedit

PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "warm": {
        "actions": {
          "forcemerge" : {
            "max_num_segments": 1
          }
        }
      }
    }
  }
}
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