@raju_ga153 welcome to the Rockstor community.
We have seen this in the past a few times on older version (and platforms), e.g. here:
And more specifically
The “POST” part here indicates that the error was during an update of the database
This is quite curios. Does your rockstor_rockstor pool look to be rw still or has it gone read only as this would cause this same issue potentially as the post (db write) would be unable to complete. Or you system drive could be low on space, but again that would have other knock-on.
Can you check the logs to see whether more details on the messsage are available? you can get to it via the WebUI, or at the command line, the file is located here:
/opt/rockstor/var/logs/rockstor.log