In the **Index Management** section, you can perform the operations available in the [Index API]({{site.url}}{{site.baseurl}}/api-reference/index-apis/index/).
[Policies]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies/) are configurations that define the possible states of an index, the actions to perform when an index enters a given state, and the conditions that must be met to transition between states:
1.**States**: The possible states of an index, including the default state for new indexes. For example, you might name your states `hot`, `warm`, or `delete`. For more information, see [States]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies/#states).
2.**Actions**: Any actions that you want the plugin to take when an index enters a given state, such as performing a rollover. For more information, see [Actions]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies/#actions).
3.**Transitions**: The conditions that must be met for an index to move into a new state. For example, if an index is more than 8 weeks old, you might want to move it to the `delete` state. For more information, see [Transitions]({{site.url}}{{site.baseurl}}/im-plugin/ism/policies/#transitions).
You have complete flexibility in designing your policies. You can create any state, transition to any other state, and specify any number of actions in each state.
5. (Optional): Specify a rollover alias if your policy includes a rollover operation. Make sure that the alias 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, Index State Management (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/).
The **Indices** section displays a list of indexes in your OpenSearch cluster. For each index, you can see its health status (`green`, `yellow`, or `red`), policy (if the index is managed by a policy), status, total size, primary sizes, total documents, deleted documents, primaries, and replicas.
While you can [create an index]({{site.url}}{{site.baseurl}}/api-reference/index-apis/create-index/) by using a document as a base, you can also create an empty index for later use.
To create an index, select the **Create Index** button located under the **Indices** section of **Index Management**. Then define the index by setting the following parameters:
- Index name
- Number of primary shards
- Number of replicas
- Refresh interval
You can also add fields and objects using either the visual editor or the JSON editor.
If you analyze time-series data, you likely want to prioritize new data over old data. You might periodically perform certain operations on older indexes, such as reducing replica count or deleting them.
[ISM]({{site.url}}{{site.baseurl}}/im-plugin/ism/index/) 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. 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 apply a policy, select the index to which you want to apply the policy from the **Indices** list under **Index Management**. Then select the **Actions** button and select **Apply policy** from the dropdown list as shown in the following image.
The [close index]({{site.url}}{{site.baseurl}}/api-reference/index-apis/close-index/) operation closes an index. Once an index is closed, you cannot add data to it or search for any data within the index.
To close an index, select the index you want to close from the **Indices** list under **Index Management**. Then select the **Actions** button and select **Close** from the dropdown list.
The [open index]({{site.url}}{{site.baseurl}}/api-reference/index-apis/open-index/) operation opens a closed index, letting you add data to it or search for data within the index.
To open an index, select the index you want to open from the **Indices** list under **Index Management**. Then select the **Actions** button and select **Open** from the dropdown list.
The [reindex]({{site.url}}{{site.baseurl}}/api-reference/document-apis/reindex/) operation lets you copy all of your data or a subset of data from a source index into a destination index.
To reindex an index, select the index from the **Indices** list under **Index Management**. Then select the **Actions** button and select **Reindex** from the dropdown list as shown in the following image.
The [shrink]({{site.url}}{{site.baseurl}}/api-reference/index-apis/shrink-index/) index operation copies all of the data in an existing index into a new index with fewer primary shards.
To shrink an index, select the index you want to shrink from the **Indices** list under **Index Management**. Then choose the **Actions** button and choose **Shrink** from the dropdown list as shown in the following image.
The [split index]({{site.url}}{{site.baseurl}}/api-reference/index-apis/split/) operation splits an existing read-only index into a new index, splitting each primary shard into a number of primary shards in the new index.
To split an index, select the index you want to split from the **Indices** list under **Index Management**. Then choose the **Actions** button and choose **Split** from the dropdown list as shown in the following image.
Refreshing an index makes new updates to the index visible to search operations.
The refresh operation can be applied only to open indexes.
To refresh all indexes, select **Refresh** from the **Actions** dropdown list.
To refresh a particular index, select the index from the **Indices** list under **Index Management**. Then select **Refresh** from the **Actions** dropdown list.
### Flushing an index
The flush operation performs a Lucene commit, writing segments to disk and starting a new translog.
The flush operation can be applied only to open indexes.
To flush all indexes, select **Flush** from the **Actions** dropdown list.
To flush a particular index, select the index from the **Indices** list under **Index Management**. Then select **Flush** from the **Actions** dropdown list.
### Clearing an index cache
The [clear cache operation]({{site.url}}{{site.baseurl}}/api-reference/index-apis/clear-index-cache/) can be applied only to open indexes.
To clear all index caches, select **Clear cache** from the **Actions** dropdown list.
To clear a particular index cache, select the index from the **Indices** list under **Index Management**. Then select **Clear cache** from the **Actions** dropdown list.
If you no longer need an index, you can use the [delete index]({{site.url}}{{site.baseurl}}/api-reference/index-apis/delete-index/) operation to delete it.
To delete an index, select the index you want to delete from the **Indices** list under **Index Management**. Then select the **Actions** button and select **Delete** from the dropdown list.
[Index templates]({{site.url}}{{site.baseurl}}/opensearch/index-templates/) let you initialize new indexes with predefined mappings and settings. For example, if you continuously index log data, you can define an index template so that all of the indexes have the same number of shards and replicas as shown in the following image.
To edit a template, select the template you want to edit from the list of templates. Next, select the **Actions** dropdown list and select the **Edit** option.
### Deleting a template
To delete a template, select the template you want to delete from the list of templates. Next, select the **Actions** dropdown list and select the **Delete** option.
An alias is a virtual index name that can point to one or more indexes. If your data is spread across multiple indexes, rather than keeping track of which indexes to query, you can create an alias and query it instead as shown in the following image.
Refreshing an alias makes new updates to the index visible to search operations.
The refresh operation can be applied only to open indexes associated with the specified aliases.
To refresh a particular alias, select the alias from the **Aliases** list under **Index Management**. Then select **Refresh** from the **Actions** dropdown list.
### Flushing an alias
The flush operation performs a Lucene commit, writing segments to disk and starting a new translog.
The flush operation can be applied only to open indexes associated with the specified aliases.
To flush an alias, select the alias from the **Aliases** list under **Index Management**. Then select **Flush** from the **Actions** dropdown list.
### Clearing an alias cache
The [clear cache operation]({{site.url}}{{site.baseurl}}/api-reference/index-apis/clear-index-cache/) can be applied only to open indexes associated with the specified aliases.
To clear an alias cache, select the alias from the **Aliases** list under **Index Management**. Then select **Clear cache** from the **Actions** dropdown list.
Certain index operations take additional time to complete (usually more than 30 seconds, but up to tens of minutes or hours). This is tracked in the index status column on the **Indices** page.
Permission control is managed with existing [permissions]({{site.url}}{{site.baseurl}}/security-plugin/access-control/permissions/) or action groups that are enforced at the API level. There is currently no UI-level permission control. Users with permission to access the ISM plugin are able to view new pages. They can also make changes if they have permission to run the related APIs.
Similar to API calls, if the operation fails immediately, you will be notified with an error message. However, if it is a long-running operation, you will be notified of the failure at the time of failure, or you can check the index status on the **Indices** page.
