Database automatically goes down

Hi all,

Our SAP version is 4.7E and OS is HP-UX and database oracle 9.2.0.7.

the problem is suddenly the database and the central instance is goes down.

when I check at os level the central and Database instance goes down.

how can I find where the problem is located?is it belongs to database or OS?

Regards,

Nani Prakash.