ADSM-L

Re: Roll Forward Mode

2001-04-17 19:41:37
Subject: Re: Roll Forward Mode
From: Nicholas Cassimatis <nickpc AT US.IBM DOT COM>
Date: Tue, 17 Apr 2001 19:41:21 -0400
I've had  a log max out at 5GB in normal - due to one very slow running
client (love those duplex mismatches!).  The client backup ran almost all
day, and we were doing some Delete Filespaces, which hit the log/db pretty
hard.  Since the log is flushed FIFO (see note), and the client session
hadn't released the DB updates as it was still running, all the updates
from the Delete Filespaces pooled up in the log.  I canceled the client
session - viola, the log went back to 0.1% utilized.

Note: The log flush to DB is done FIFO to keep the order of transactions in
place.  This can be important, since copying and updating a record in
reverse order can cause the data to become inaccurate (read corrupt).  If I
copy a record, then update the original, the copy and original are now
different.  However, if I push the update action before the copy, they are
the same, in the updated state.  Obviously a very bad thing if you like
data integrity.

Nick Cassimatis
nickpc AT us.ibm DOT com
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