I have a datalogging application installed at around 80 sites running
24x7 on CentOS 5, FB 2.1.4 Classic. There are typically 2 or 3 clients,
one of which is constantly acquiring data and storing it in the
database. The database is usually 2-3GB.

This is all working extremely well, but I have noticed that very
occasionally when the main application tries to store some data I get an
error -902 "cannot attach to password database". Since it's not system
critical that the write fails, the software just logs the error and
continues working. The same code will be called again within a few
seconds and will almost certainly work next time. Days or even a couple
of weeks can pass without this error showing up again.

One further detail which may or may not be important. The database is
backed up hourly with nbackup (monthly, daily, hourly backups) and the
error mostly seems to occur within a minute of the nbackup process
finishing although this isn't the only time it happens.

Thankfully the error isn't really a problem, but can anyone give me a
clue what might be causing it and how I can fix it?

Regards,

Tom Munro Glass