Messing around with base tables is not supported - best to raise an SR with Support
There is a standard process for purging old workflow notifications - you should use that rather that truncating the base tables.
The right thing to do for the purification of notifications is to run a concurrent purge items workflow.
This is necessary because it erases all the links that notification being purged.
Here in the company where I advise perform cleaning of the notifications every 90 days.
I hope this helps
Thank you all for all your inputs, we did restored table from DR with help of Oracle.