Splunk SPLK-2002 - Splunk Enterprise Certified Architect

The license_usage.log file is generated and maintained on the License Manager node in a Splunk deployment. This log provides detailed statistics about daily license consumption, including data volume indexed per pool, index, sourcetype, source, and host.

In a distributed or clustered environment (with both search head and indexer clusters), the License Manager acts as the central authority that collects license usage information from all indexers and consolidates it into this log. The License Manager receives periodic reports from each license peer (indexer) and records them in:

$SPLUNK_HOME/var/log/splunk/license_usage.log

The log is automatically indexed into the _internal index with sourcetype=splunkd and can be queried using searches such as:

index=_internal source=*license_usage.log* type="RolloverSummary"

Other components like the Cluster Manager, SHC Deployer, or individual indexers do not store the full consolidated license usage data — they only send summarized reports to the License Manager.

Therefore, the License Manager is the definitive and Splunk-documented location for retrieving and analyzing license_usage.log data across a distributed deployment.

References (Splunk Enterprise Documentation):

• Managing Licenses in a Distributed Environment

• license_usage.log Reference and Structure

• Monitoring License Consumption Using the License Manager

• Splunk Enterprise Admin Manual – License Reporting and Troubleshooting

Number of concurrent users: This is an important factor because it affects the search performance and resource utilization of the Splunk environment. More users mean more concurrent searches, which require more CPU, memory, and disk I/O. The number of concurrent users also determines the search head capacity and the search head clustering configuration12

Volume of incoming data: This is another crucial factor because it affects the indexing performance and storage requirements of the Splunk environment. More data means more indexing throughput, which requires more CPU, memory, and disk I/O. The volume of incoming data also determines the indexer capacity and the indexer clustering configuration13

Existence of premium apps: This is a relevant factor because some premium apps, such as Splunk Enterprise Security and Splunk IT Service Intelligence, have additional requirements and recommendations for the Splunk environment. For example, Splunk Enterprise Security requires a dedicated search head cluster and a minimum of 12 CPU cores per search head. Splunk IT Service Intelligence requires a minimum of 16 CPU cores and 64 GB of RAM per search head45

 Configurations from the deployer are merged into the SPLUNK_HOME/etc/apps/APP_HOME/local directory on the search head cluster member. The deployer distributes apps and other configurations to the search head cluster members in the form of a configuration bundle. The configuration bundle contains the contents of the SPLUNK_HOME/etc/shcluster/apps directory on the deployer. When a search head cluster member receives the configuration bundle, it merges the contents of the bundle into its own SPLUNK_HOME/etc/apps directory. The configurations in the local directory take precedence over the configurations in the default directory. The SPLUNK_HOME/etc/system/local directory is used for system-level configurations, not app-level configurations. The SPLUNK_HOME/etc/apps/search/default directory is used for the default configurations of the search app, not the configurations from the deployer.

All of the options are possible causes of a crash in Splunk. According to the Splunk documentation1, incorrect ulimit settings can lead to file descriptor exhaustion, which can cause Splunk to crash or hang. Insufficient disk IOPS can also cause Splunk to crash or become unresponsive, as Splunk relies heavily on disk performance2. Insufficient memory can cause Splunk to run out of memory and crash, especially when running complex searches or handling large volumes of data3. Running out of disk space can cause Splunk to stop indexing data and crash, as Splunk needs enough disk space to store its data and logs4.

1: Configure ulimit settings for Splunk Enterprise 2: Troubleshoot Splunk performance issues 3: Troubleshoot memory usage 4: Troubleshoot disk space issues

The site_mappings attribute should be added to the master node’s server.conf file when decommissioning a site in an indexer cluster. The site_mappings attribute is used to specify how the master node should reassign the buckets from the decommissioned site to the remaining sites. The site_mappings attribute is a comma-separated list of site pairs, where the first site is the decommissioned site and the second site is the destination site. For example, site_mappings = site1:site2,site3:site4 means that the buckets from site1 will be moved to site2, and the buckets from site3 will be moved to site4. The available_sites attribute is used to specify which sites are currently available in the cluster, and it is automatically updated by the master node. The site_search_factor and site_replication_factor attributes are used to specify the number of searchable and replicated copies of each bucket for each site, and they are not affected by the decommissioning process

According to the Splunk documentation1, the “Unknown sid” error message means that the search job associated with the link has expired or been deleted. The sid (search ID) is a unique identifier for each search job, and it is used to retrieve the results of the search. If the sid is not found, the search cannot be displayed. The other options are false because:

The users having insufficient permissions would result in a different error message, such as “You do not have permission to view this page” or "You do not have permission to run this search"1.

An add-on needing to be updated would not affect the validity of the sid, unless the add-on changes the search syntax or the data source in a way that makes the search invalid or inaccessible1.

One or more indexers being down would not cause the “Unknown sid” error, as the sid is stored on the search head, not the indexers. However, it could cause other errors, such as “Unable to distribute to peer” or "Search peer has the following message: not enough disk space"1.

 A multi-site indexer cluster can be configured by directly editing SPLUNK_HOME/etc/system/local/server.conf or running a splunk edit cluster-config command from the CLI. These methods allow the administrator to specify the site attribute for each indexer node and the site_replication_factor and site_search_factor for the cluster. Configuring a multi-site indexer cluster via Splunk Web or directly editing SPLUNK_HOME/etc/system/default/server.conf are not supported methods. For more information, see Configure the indexer cluster with server.conf in the Splunk documentation.

According to Splunk’s Enterprise Security (ES) Installation and Sizing Guide, the majority of processing and computational load generated by the Splunk App for Enterprise Security is concentrated on the Search Head(s).

This is because Splunk ES is built around a search-driven correlation model — it continuously runs scheduled correlation searches, data model accelerations, and notables generation jobs. These operations rely on the search head tier’s CPU, memory, and I/O resources rather than on indexers. ES also performs extensive data model summarization, CIM normalization, and real-time alerting, all of which are search-intensive operations.

While indexers handle data ingestion and indexing, they are not heavily affected by ES beyond normal search request processing. The Cluster Manager only coordinates replication and plays no role in search execution, and Heavy Forwarders serve as data collection or parsing points with minimal analytical load.

Splunk officially recommends deploying ES on a dedicated Search Head Cluster (SHC) to isolate its high CPU and memory demands from other workloads. For large-scale environments, horizontal scaling via SHC ensures consistent performance and stability.

References (Splunk Enterprise Documentation):

• Splunk Enterprise Security Installation and Configuration Guide

• Search Head Sizing for Splunk Enterprise Security

• Enterprise Security Overview – Workload Distribution and Performance Impact

• Splunk Architecture and Capacity Planning for ES Deployments

 When adding or rejoining a member to a search head cluster, and the following error is displayed: Error pulling configurations from the search head cluster captain; consider performing a destructive configuration resync on this search head cluster member.

The corrective action that should be taken is to run the splunk resync shcluster-replicated-config command on this member. This command will delete the existing configuration files on this member and replace them with the latest configuration files from the captain. This will ensure that the member has the same configuration as the rest of the cluster. Restarting the search head, running the splunk apply shcluster-bundle command from the deployer, or running the clean raft command on all members of the search head cluster are not the correct actions to take in this scenario. For more information, see Resolve configuration inconsistencies across cluster members in the Splunk documentation.

According to the Indexer Clustering Administration Guide, configuration bundles pushed from the Cluster Manager (Master Node) overwrite the contents of the $SPLUNK_HOME/etc/slave-apps/ directory on each search peer (indexer). However, Splunk provides a special persistent location — the _cluster app’s local directory — for files that must survive bundle redeployments.

Specifically, any configuration files placed in:

$SPLUNK_HOME/etc/slave-apps/_cluster/local/

will persist after future bundle pushes because this directory is excluded from the automatic overwrite process.

This is particularly useful for maintaining local overrides or custom configurations that should not be replaced by the Cluster Manager, such as environment-specific inputs, temporary test settings, or monitoring configurations unique to that peer.

Other directories under slave-apps are overwritten each time a configuration bundle is pushed, ensuring consistency across the cluster. Likewise, master-apps exists only on the Cluster Manager and is used for deployment, not persistence.

Thus, the _cluster/local folder is the only safe, Splunk-documented location for configurations that need to survive bundle redeployment.

References (Splunk Enterprise Documentation):

• Indexer Clustering: How Configuration Bundles Work

• Maintaining Local Configurations on Clustered Indexers

• slave-apps and _cluster App Structure and Behavior

• Splunk Enterprise Admin Manual – Cluster Configuration Management Best Practices