Indices enter phases based on a phase’s min_age parameter. The index will not enter the phase until the index’s age is older than that of the min_age. The parameter is configured using a time duration format (see Time Units).

min_age defaults to zero seconds 0s for each phase if not specified.

PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "warm": {
        "min_age": "1d",
        "actions": {
          "allocate": {
            "number_of_replicas": 1
          }
        }
      },
      "delete": {
        "min_age": "30d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}

The Above example configures a policy that moves the index into the warm phase after one day. Until then, the index is in a waiting state. After moving into the warm phase, it will wait until 30 days have elapsed before moving to the delete phase and deleting the index.

min_age is usually the time elapsed from the time the index is created. If the index is rolled over, then min_age is the time elapsed from the time the index is rolled over. The intention here is to execute following phases and actions relative to when data was written last to a rolled over index.

The previous phase’s actions must complete before index lifecycle management will check min_age and transition into the next phase.