I have had the same error this month while exporting to csv using outputcsv command. The problem was related actually to free disk space but not logged in Splunk log files! I think that Splunk is using multiphase mechanism to accomplish indexing jobs; that’s why it needs more than double free space of the expected results size.
I have monitored the directory %SPLUNK%\var\run\splunk . There were many .LOCK files eating disk space while indexing job was running.
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