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Set up multiple indexes

Splunk ships with an index called main that, by default, holds all your events. By default, Splunk also creates a number of other indexes for use by its internal systems, as well as for additional Splunk features such as summary indexing and event auditing.

Splunk with an Enterprise license lets you add an unlimited number of additional indexes. The main index serves as the default index for any input or search command that doesn't specify an index, although you can change the default. You can add indexes using Splunk Web, Splunk's CLI, or indexes.conf.

Why have multiple indexes?

There are several key reasons for having multiple indexes:

  • To control user access.
  • To accommodate varying retention policies.
  • To speed searches in certain situations.

The main reason you'd set up multiple indexes is to control user access to the data that's in them. When you assign users to roles, you can limit user searches to specific indexes based on the role they're in.

In addition, if you have different policies for retention for different sets of data, you might want to send the data to different indexes and then set a different archive or retention policy for each index.

Another reason to set up multiple indexes has to do with the way Splunk search works. If you have both a high-volume/high-noise data source and a low-volume data source feeding into the same index, and you search mostly for events from the low-volume data source, the search speed will be slower than necessary, because Splunk also has to search through all the data from the high-volume source. To mitigate this, you can create dedicated indexes for each data source and route data from each source to its dedicated index. Then, you can specify which index to search on. You'll probably notice an increase in search speed.

Specify an index or indexes to search

When Splunk searches, it targets the default index (by default, main) unless otherwise specified. If you have created a new index, or want to search in any index that is not default, you can specify the index in your search:

index=hatch userid=henry.gale

This searches in the hatch index for the userid=henry.gale.

You can also specify an alternate default index for a given role to search when you create or edit that role.

Create and edit indexes

You can create or edit indexes with Splunk Web, the Splunk CLI, or directly, via indexes.conf.

Use Splunk Web

1. In Splunk Web, navigate to Manager > Indexes and click New.

2. To create a new index, enter:

  • A name for the index. User-defined index names must consist of only numbers, lowercase letters, underscores, and hyphens. They cannot begin with an underscore or hyphen.
  • The path locations (all optional, will default to be rooted in $SPLUNK_DB/<index_name>/):
    • Home path; leave blank for default $SPLUNK_DB/<index_name>/db
    • Cold db path; leave blank for default $SPLUNK_DB/<index_name>/colddb
    • Thawed/resurrected db path, leave blank for default $SPLUNK_DB/<index_name>/thaweddb
  • The maximum size (in MB; optional) of the entire index. Defaults to 500000MB.
  • The maximum size (in MB; optional) of the hot (currently actively searched) portion of this index. When setting the maximum size, you should use "auto_high_volume" for high volume indexes (such as the main index); otherwise, use "auto".
  • The frozen archive path (optional). Set this field if you want Splunk to archive frozen buckets. For information on bucket archiving, see "Archive indexed data".

3. When you've set the values you want, click Save. The index is created.

You can edit an index by clicking on the index name in the Indexes section of Manager in Splunk Web. Properties that you cannot change are grayed out. To change these properties, edit indexes.conf. You must restart Splunk if you edit the properties of an existing index.

Note: Some index properties are configurable only when you create or edit indexes with the indexes.conf file. Check the indexes.conf topic for a complete list of properties.

Use the CLI

Navigate to the $SPLUNK_HOME/bin/ directory and use the add index command. You do not need to stop Splunk first.

To add a new index called "fflanda", enter the following command:

splunk add index fflanda

Note: User-defined index names must consist of only numbers, lowercase letters, underscores, and hyphens. They cannot begin with an underscore or hyphen.

If you do not want to use the default path for your new index, you can use parameters to specify a new location:

./splunk add index foo -homePath /your/path/foo/db -coldPath /your/pat/foo/colddb
    -thawedPath /your/path/foo/thawedDb

You can also edit an index's properties from the CLI. For example, to edit an index called "fflanda" using the CLI, type:

splunk edit index fflanda -<parameter> <value>

Edit indexes.conf

To add a new index, add a stanza to indexes.conf in $SPLUNK_HOME/etc/system/local, identified by the name of the new index. See configuration details and examples in the indexes.conf topic.

Note: The index name, specified in the stanza, must consist of only numbers, lowercase letters, underscores, and hyphens. User-defined index names cannot begin with an underscore or hyphen.

You must restart Splunk to enable configuration changes.

Important: When creating a new index, the maximum number of hot buckets now defaults to 3. (Prior to version 4.2, the default was 1.) To change this, set the maxHotBuckets attribute in the new index's stanza in indexes.conf.

Disable an index

You can disable an index in Splunk Web. To do this, navigate to Manager > Indexes and click Disable to the right of the index you want to disable.

To delete an index or the data in the index, see "Remove indexed data from Splunk" in this manual.

Route events to specific indexes

Just as you can route events to specific queues, you can also route events to specific indexes.

By default, Splunk sends all events to the index called main. However, you may want to send specific events to other indexes. For example, you might want to segment data or to send event data from a noisy source to an index that is dedicated to receiving it. You can route data locally or route data you are receiving from remote sources or Splunk instances.

Note: When you place data in an alternate index, you must specify the index in your search with the index= command when you want to search that index:


Send all events from a data input to a specific index

To configure routing for all events from a particular data input to an alternate index, add the following to the appropriate stanza in inputs.conf.

index = myindex

The following example inputs.conf entry routes data to index = fflanda:

disabled = false
index = fflanda

If you specify a different index on a forwarder, when the events reach the indexing instance they will be routed to the named index, which must already exist.

Route specific events to a different index

To route certain events to an alternate index, edit props.conf and transforms.conf on the local Splunk instance:

1. Identify a common attribute for the events that can be used to differentiate them.

2. In props.conf, create a stanza for the source, source type, or host. This stanza specifies a transforms_name that corresponds to a regex-containing stanza you will create in transforms.conf.

3. In transforms.conf, create an stanza named with the transforms_name you specified in step 2. This stanza:

  • Specifies a regular expression that matches the identified attribute from step 1.
  • Specifies the alternate index that events matching the attribute should be routed to.

The sections below fill out the details for steps 2 and 3.

Edit props.conf

Add the following stanza to $SPLUNK_HOME/etc/system/local/props.conf:

TRANSFORMS-<class_name> = <transforms_name>

Note the following:

  • <spec> is one of the following:
    • <sourcetype>, the sourcetype of an event
    • host::<host>, where <host> is the host for an event
    • source::<source>, where <source> is the source for an event
  • <class_name> is any unique identifier.
  • <transforms_name> is whatever unique identifier you want to give to your transform in transforms.conf.

Edit transforms.conf

Add the following stanza to $SPLUNK_HOME/etc/system/local/transforms.conf:

REGEX = <your_custom_regex>
DEST_KEY = _MetaData:Index
FORMAT = <alternate_index_name>

Note the following:

  • <transforms_name> must match the <transforms_name> identifier you specified in props.conf.
  • <your_custom_regex> must provide a match for the attribute you identified earlier.
  • DEST_KEY must be set to the index attribute _MetaData:Index.
  • <alternate_index_name> specifies the alternate index that the events will route to.


In this example, we route events of windows_snare_log sourcetype to the appropriate index based on their log types. "Application" logs will go to an alternate index, while all other log types, such as "Security", will go to the default index.

To make this determination, we use props.conf to direct events of windows_snare_log sourcetype through the transforms.conf stanza named "AppRedirect", where a regex then looks for the log type, "Application". Any event with a match on "Application" in the appropriate location is routed to the alternate index, "applogindex". All other events go to the default index.

Identify an attribute

The events in this example look like this:

web1.example.com	MSWinEventLog	1	Application	721	Wed Sep 06 17:05:31 2006
4156	MSDTC	Unknown User	N/A	Information	WEB1	Printers		String
message: Session idle timeout over, tearing down the session.	179

web1.example.com	MSWinEventLog	1	Security	722	Wed Sep 06 17:59:08 2006
576	Security	SYSTEM	User	Success Audit	WEB1	Privilege Use
Special privileges assigned to new logon:     User Name:      Domain:      Logon
ID: (0x0,0x4F3C5880)     Assigned: SeBackupPrivilege   SeRestorePrivilege
SeDebugPrivilege   SeChangeNotifyPrivilege   SeAssignPrimaryTokenPrivilege 525

Some events contain the value "Application", while others contain the value "Security" in the same location.

Edit props.conf

Add this stanza to $SPLUNK_HOME/etc/system/local/props.conf:

TRANSFORMS-index = AppRedirect

This directs events of windows_snare_syslog sourcetype to the AppRedirect stanza in transforms.conf.

Edit transforms.conf

Add this stanza to $SPLUNK_HOME/etc/system/local/transforms.conf:

REGEX = MSWinEventLog\s+\d+\s+Application
DEST_KEY = _MetaData:Index
FORMAT = applogindex

This stanza processes the events directed here by props.conf. Events that match the regex, by containing the string "Application" in the specified location, get routed to the alternate index, "applogindex". All other events route to the default index.

About managing indexes
Set limits on disk usage

This documentation applies to the following versions of Splunk® Enterprise: 4.3, 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.3.6, 4.3.7

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