Journaling usage

On Fri, 6 Sep 1996, FSDTEAM wrote:

> Currently we are not using the Journaling option in Ingres. As all the
> Ingres sites i've worked at in the past have not used journaling, I'm
> relying on the DBA manual (shock/horror).
> >From what I can gather the only thing to do is to enable journaling on
> our tables and do a chkpt with the +J flag. From a performance point of
> view I assume the journal file should be on its own disk.
> IS THERE ANYTHING ELSE TO CONSIDER ????? please help.

Maybe lots more (it depends).  Here's the basic recipe:

  1. SET JOURNALING on all the tables you want to journal.  (I will argue 
     if you want to journal ONE table you want to journal them ALL--unless
     the table is a STRICTLY temporary table that you routinely 
     truncate/destroy and reload.)
  2. Do a ckpdb +j to start writing journal files.
  3. Periodically do a ckpdb -d to clear out stale journal files.

You want your journal files on a separate drive from the database for 
recovery purposes, not performance.  The journal files are written 
asynchronously and only the busiest systems will notice the load.
You certainly don't want to find that a single disc failure has destroyed 
both the database AND the journal files you need to recover the 
database.  It is probably acceptable to have the journal files and the 
checkpoints on the same device--you can't use the journals without the 
checkpoints.  On the other hand the journal files can be allowed to occupy 
more space if they have a file system to themselves.

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Roy Hann                                   rhann@tnc.com
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