Getting a snapshot too old error 1555 from batch job on first query it executes

Hi,

I have a batch job, started by an other batch job.

And the first action of the procedure that is executed is opening a cursor, doing a select for update nowait.

Before the result of the fetch is processed the program gets aborted throwing a snapshot too old error.

This program worked when we were on version 11.2, but after upgrading to 12.1 this behavior is started happening.

It does not occur all the time. It runs every minute and fails on average once every hour. (no clear time pattern found)

Any ideas what this could cause?

HansL