Hi
Kindly increase the size under the below parameter and restart the splunk services.
Under the server.conf
[queue]
maxSize
Kindly, check for which specific indexes and for which bucket directories it is giving the error.
Generally, whenever an index generates too many small tsidx files(more than 25) Splunk is not able to optimize all those files within the specified time period.
Kindly, run the below command against the specific directory to optimize it manually:-
splunk-optimize -d|--directory
Or you can make the below changes in Indexes.conf to fix the issue:-
[default]
maxConcurrentOptimizes=25
maxRunningProcessGroups=12
processTrackerServiceInterval=0
Please go through the below documentation to have a better understanding of Splunk Optimization.
http://docs.splunk.com/Documentation/Splunk/latest/Indexer/Optimizeindexes
Try running the splunk-optimize process manually against that directory: http://docs.splunk.com/Documentation/Splunk/latest/Indexer/Optimizeindexes
Also, make sure you haven't changed the value of maxConcurrentOptimizes in indexes.conf from its default value.