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Message Posted: Mon, 20 Jun 2005 @ 15:58:00 GMT

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Subj:   Re: Dbscontrol - Cylinder Saved for Perm
From:   Dennis Calkins

On Mon, 20 Jun 2005 08:55:46 -0400, Anomy Anom wrote:

  I am looking for simple meaning of dbscontrol parameter( Cylinder Saved for Perm ), is this is anyway related to Defrag and MiniCyl ?  


Saved for Perm simply reserves X number of cylinders that can only be used for PERM Tables. Therefore if the system ever gets to X cylinders free all Requests for SPOOL cylinders will be rejected.

Now its relation to MINICYLPACK is that when a request is rejected we will kick off a minicylpack to try and free up 1 cylinder beyond 'X' to allow us to satisfy the request on a second attempt at allocation. While this type of minicylpack is going on the transaction is stalled waiting for Minicylpack to complete.

If we complete a MINICYLPACK pass without being able to free up that 'X+1'th cylinder, we then abort the transaction which will hopefully FREE up all the SPOOL cylinders in use by that transaction.

There are a couple other parameters controlling Defrag and Minicylpacks in Preemptive mode rather than in 'OUT' mode.

     2.  MiniCylPackLowCylProd    = 10 (free cylinders)

This values mean when we get within 10 Cylinders of 'X' we will try a Preemptive Minicylpack in an attempt to free up a cylinder so that we can prevent ourselves from reaching 'X' cylinders free.

A preemptive Minicylpack stops when it has freed a cylinder or has accessed 10 cylinders. Transactions do NOT get stalled during preemptive Minicylpacks.

     5.  DefragLowCylProd         = 100 (free cylinders)

This value mean when we get within 100 Cylinders of 'X' we will try to DEFRAG cylinders in an attempt to free up some space with a cylinder so that we can add more data to that cylinder in the future. Transactions are NEVER stalled during DEFRAG operations.

You can tell if you are getting Defrags and Minicylpacks going on your system by checking your /var/adm/streams log on MPRAS or the event viewer on Windows.

5141 Mini-Cylinder Pack freed cylinders in anticipation of their use

5142 Mini-Cylinder Pack freed cylinders while tasks were waiting for them

5143 Mini-Cylinder Pack was not able to free any cylinders

5166 Defragment of cylinder[s] occurred

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