Hi Lahiru,
maybe your node was running out of memory before. I saw this behaviour
if available heap is low forcing to flush out memtables to sstables
quite often.
If this is that what is hitting you, you should see that the sstables
are really small.
To cleanup, nodetool compact would do the job - but if you do not need
data from one of the keyspaces at all just drop and recreate it (but
look into your data directory if there are snapshots left). Prevent this
in future have a close look at heap consumption and maybe give it more
memory.
HTH,
Jan
