Hi Khushaboo,
It is very difficult to say why it is happening but can be due any of the reasons below.
- Transient error due to network issues.
- Network latency causing timeouts with database.
- Also check on the latest fixes available on IS , just to avoid any issues due to the same.
- Check on the database server logs whenever this error happens, might be you get more info to troubleshoot this.
Regards,
Firoz N