Inbound IDOC messages Retention Period- Where to Check

Hi Gurus,

Where do we specify Inbound IDOC messages rention period.

In our system I do not see Inbound IDOC messages ( coming from ECC to PI) older than 15 days.

But I see Outbound IDOC messages ( PI to ECC) older than 15 days.Also I see non IDOC messages older than 15 days.

I checked in SXMB_ADM, Integration Engine Configuration and I do not see any parameter for IDOCS.

I appreciate any pointers.

Regards,

Ramesh.