If you analyze time-series data, you likely prioritize new data over old data. You might periodically perform certain operations on older indices, such as reducing replica count or deleting them.
Index State Management (ISM) is a plugin that lets you automate these periodic, administrative operations by triggering them based on changes in the index age, index size, or number of documents. Using the ISM plugin, you can define *policies* that automatically handle index rollovers or deletions to fit your use case.
For example, you can define a policy that moves your index into a `read_only` state after 30 days and then deletes it after a set period of 90 days. You can also set up the policy to send you a notification message when the index is deleted.
You might want to perform an index rollover after a certain amount of time or run a `force_merge` operation on an index during off-peak hours to improve search performance during peak hours.
To use the ISM plugin, your user role needs to be mapped to the `all_access` role that gives you full access to the cluster. To learn more, see [Users and roles]({{site.url}}{{site.baseurl}}/security-plugin/access-control/users-roles/).
A policy is a set of rules that describes how an index should be managed. For information about creating a policy, see [Policies]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies/).
You can use the JSON editor or visual editor to create policies. Compared to the JSON editor, the visual editor offers a more structured way of defining policies by separating the process into creating error notifications, defining ISM templates, and adding states. We recommend using the visual editor if you want to see pre-defined fields, such as which actions you can assign to a state or under what conditions a state can transition into a destination state.
4. In the **Name policy** section, enter a policy ID.
5. In the **Define policy** section, enter your policy.
6. Choose **Create**.
After you create a policy, your next step is to attach it to an index or indices.
You can set up an `ism_template` in the policy so when an index that matches the ISM template pattern is created, the plugin automatically attaches the policy to the index.
For an example ISM template policy, see [Sample policy with ISM template]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies#sample-policy-with-ism-template).
Older versions of the plugin include the `policy_id` in an index template, so when an index is created that matches the index template pattern, the index will have the policy attached to it:
The `opendistro.index_state_management.policy_id` setting is deprecated. You can continue to automatically manage newly created indices with the ISM template field.
{: .note }
### Step 2: Attach policies to indices
1. Choose **Indices**.
2. Choose the index or indices that you want to attach your policy to.
3. Choose **Apply policy**.
4. From the **Policy ID** menu, choose the policy that you created.
You can see a preview of your policy.
5. If your policy includes a rollover operation, specify a rollover alias.
Make sure that the alias that you enter already exists. For more information about the rollover operation, see [rollover]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies#rollover).
After you attach a policy to an index, ISM creates a job that runs every 5 minutes by default to perform policy actions, check conditions, and transition the index into different states. To change the default time interval for this job, see [Settings]({{site.url}}{{site.baseurl}}/im-plugin/ism/settings/).
Make sure that the alias that you enter already exists. For more information about the rollover operation, see [rollover]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies#rollover).
