Hi Chandrashekar,
> Please suggest after deleting the old statistics which actions required.
Depends on what you try to achieve? Do you want to reclaim the corresponding space? MOS note #454678.1 describes this procedure for example ... or you can apply bugfix / enhancement #10279045 and use it.
You can also check the mmon trace files for time-outs like "Runtime exceeded 300 seconds". This would explain the very long statistic history, even if the retention period is set to 31 days.
The mmon process is only given 5 minute to complete the automatic purging of optimizer statistics data. If it has not finished in that time then it aborts and does not produce any sort of error message or trace information. Data has built up because excessive amounts have been created due to a rogue programme and the mmon process has spent 5 minutes every day for a year in trying to remove that excess but has failed miserably and not told anybody about it.
So the question would be (if you hit that issue) - why do i generate that amount of data? In my experience it is based on a bad configured statistic job (brconnect) or you collect / maintain a lot of histograms.
Regards
Stefan