> On one of our databases using Firebird 2.0.1.12855
> with a database size 250GB we get the below error:
>
> internal gds software consistency check (pointer page vanished from
> DPM_next (249), file: dpm.cpp line: 1609)

Sad

Does you have server crashes or out of disk space conditions ?
What is in your firebird.log ?
Does you run gfix -v -f ?

> How can this happen and how can it be fixed?

If its really happens i doubt it can be fixed by gfix. You may ask ib_aid
team for more advanced diagnos (its free) and possible repair (its not free).

Regards,
Vlad