This page assists with step on how to move the CSS data files to a new file system when faced with messages like this:
ERROR: could not extend file "base/12401/557501": No space left on device
HINT: Check free disk space.
This message can be in the analysis log, but will also be in the postgres log. For finding the logs, please see this page: CAST Management Studio - Information - How to find logs
The analysis log message may be not as clear showing the problem with no space left on the device and may show something like this:
Procedure call failed: ?<kb_name>.CACHE_FLUSHDATA,I_IDSESSION
but still will show the space error in the postgres log.
For more information on CSS, refer to: