Subject RE: [Firebird-Architect] WAL and JOURNAL
Author Samofatov, Nickolay
Hi, Dave!

> Yes, I was revering to the WAL related items (4 bytes? 8 bytes? can't
> recall) in the page header. Since a new ODS is coming anyway, yank
> those as well (with, perhaps, reserving 4 bytes for "future work").

These are

ULONG pag_seqno; /* WAL seqno of last
update */
ULONG pag_offset; /* WAL offset of last
update */

When WAL is not enabled I use 4 bytes at pag_seqno address for backup
event sequence number needed to collect recent changes for incremental
backup purposes. We may rename pag_seqno to pag_scn and kill ULONG&
pag_scn() { return pag_seqno; } function from struct pag.

AFAIR, there are some WAL-related bytes in database header that need to
be set in ODS10 database with WAL disabled to be usable by IB6/FB1/FB15.
I don't remember exactly, but Yaffil people stepped on that problem when
cleaned out WAL initially. I think Dmitry may clear the matters here.

> Dave