Warning Mess when DB startup

Dear Team,

I am new to DB2 .We are using DB2 9.7 for SAP. when starting up DB we are facing a warning message like

Database activated

*** WARNING Logretain mode is disabled

You will be unable to fully recover your database in case

of a media failure

Starting Startup Agent sapstartsrv.

I checked the LOGRETAIN value = NO.

Can you please help me how to change this parameter and what value i should maintain to get the archieve logs.

Thanks,
Thamodaran.