Usually the data pages are get corrupted because they are far more
than the data pages that keeps metadata, but in this case I guess -
the datapages for metadata are corrupted. I know one - almost real
folk story - about such case. Then the developer acquired knowledge
about ODS (OnDiskStructre) of fdb file and he managed to find and
correct some byte that caused such errors. Usually there is no more
than some incorrect bytes. There are some programms that - for at
lest to Interbase - could display the fdb content as set of records
and so on, IBSurgeon was one of them. BTW - for C++ programmer this
can be not so big issue.

--- In firebird-support@yahoogroups.com, "Adam" <s3057043@...> wrote:
>
> --- In firebird-support@yahoogroups.com, Ahmad $arhan ****
> <mahdoom_a@> wrote:
> >
> > Dear all,
> >
> > my problem is getting worst, in addition to the prevoius sql
error
> i am getting this when i tried to back-up and restore DB, please
help me
> >
> > select rc.rdb$constraint_name,
> > i.rdb$field_name
> > from rdb$relation_constraints rc, rdb$index_segments i
> > where (i.rdb$index_name = rc.rdb$index_name) and
> > (rc.rdb$constraint_type = 'PRIMARY KEY')
> > and (rc.rdb$relation_name = 'RLSTT')
> > order by i.rdb$field_position
> >
> > Unsuccessful execution caused by a system error that precludes
> > successful execution of subsequent
> > statements.
> > internal gds software consistency check (can't continue after
bugcheck).
> >
> > select RDB$RELATION_NAME, RDB$SYSTEM_FLAG
> > , RDB$DESCRIPTION
> > from RDB$RELATIONS where (RDB$VIEW_SOURCE is NULL)
> > and (RDB$SYSTEM_FLAG = 0)
> > order by RDB$RELATION_NAME
> > Unsuccessful execution caused by a system error that precludes
> > successful execution of subsequent
> > statements.
> > database file appears corrupt ().
> > bad checksum.
> > checksum error on database page 39243.
>
> This seems to me to be a simple case of database corruption.
Database
> corruption is extremely unusual unless you are mishandling the
> database files.
>
> Gfix may help, or even try a simple backup using the -g switch. If
the
> corruption is in a page that contains no useful data, then you may
be
> lucky and can take a working backup by avoiding the normal garbage
> collection during the backup.
>
> Adam
>