I just noticed a detail that I don't like.
We had an error logged in the alert log. It informed me that details were in
db_ckpt_1234.log. Fine, but there was no such log in the bdump directory.
The dba who was here before me wrote a nice script to run every Sunday to clean up old trace files. What he didn't think of is that the trace files seem to be written per session, and that the checkpoint 'session' continues from instance start up.
His script came along and happily moved the trace file to a backup_bdump directory. Oracle couldn't find it and didn't write the details.
One more fix to make.
A few basic notes on Oracle Database Administration.