From: Aaron Morris (aaronmorris@MINDSPRING.COM)
Date: Wed Oct 16 2002 - 13:51:47 EDT
If I understand JFS correctly, it doesn't log (journal) data itself,
only the meta-data (time-stamps, filename, etc.). Data is not committed
in the transaction, data is written to the filesystem whenever a write
operation occurs (not taking FS/drive/controller cache into account).
Every few seconds the meta-data is committed, this is why you could
potentially lose the entire contents of a file if the power is lost
before a meta-data commit occurs.
JFS and JFS2 cannot journal data.
-Aaron Morris
justin.bleistein@SUNGARD.COM wrote:
> I'm a bit of an Oracle database beginner DBA and from what I
> understand from reading from books and doing exercises on my mock database
> is that the definition of a log, is when a transaction is made it's not
> committed it can always be rolled back. So If I don't have Oracle:
> "autocommit" turned on then I use the "insert data" command to insert data
> a column into a table, if I then type in rollback;. then the logs will
> replay the way that table looked before that column was inserted with the
> "insert data" was issued so the column isn't there. OK? Now that knowledge
> is out of the way I'm looking at AIX the same way it has a JFS log. Now
> from what I understand it holds all filesystem transaction changes. If this
> is true, Is it possible for me to roll it back like with a replay or
> rollback command just like in a database such as Oracle?. If so would a
> good sinerio to use this be when you create a file you don't want you can
> replay the log to replay the way it looked without that file?. If so what
> are the commands to manage JFS and recreate the filesystems using the log.
> For DR it would be a great tool to be able to just replay the JFS logs, to
> rebuild them the way they looked in Production. I'm pretty sure mksysb and
> sysback actually replays the JFS logs to recreate there Fs's during a
> restore. What's the command? Can this be done from the command line, or is
> this just an operating system thing?. Also this would be good for tuning
> TSM to be an actual BMR solution to have scripts which replay JFS logs. In
> Oracle you as the DBA have complete control as too replaying the logs to
> recover from unwanted data. Do you have that same control as an AIX ADMIN
> to recover from FS's oopss, or recreations in DR? Thanks and sorry for the
> novel.
>
> --Justin
>
This archive was generated by hypermail 2.1.7 : Wed Apr 09 2008 - 22:16:16 EDT