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Message Posted: Thu, 10 Oct 2002 @ 06:07:20 GMT


     
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Subj:   Re: Usage of Ferret/packdisk
 
From:   Dennis Calkins

Packdisk does not need to be run on spool. Spool is built in nice 64K/128K blocks layed down in a row so there is no fragmentation and therefore nothing to pack.

There is a new command in ferret for 4.1 called

showfsp

It allows you to pretend you are running a packdisk and it will estimate how many cylinders would be reclaimed from each table after the packdisk was done if you actually did the packdisk.

if you want to simulate a

packdisk fsp = 15

you would issue

showfsp -d 15

I recommend running it on a single AMP

scope vproc 0

since amps are probably fragmented equally. If you want you could pick a couple amps

scope vproc ( 0, 5, 10, 15, 20 , 25, 30 )

and compare the results. here is a sample result.

1:vproc  15 (000F)  response
1:
1:There are  2 tables larger than 45 cylinders on amp 15
1:
1:Database    Table                     fsp   Recoverable Current
1:Name        Name                       %    Cylinders   Cylinders
1:----------- ------------------------- ----- ----------- -------
1:Crashdumps  Crash_20010223_155740_09   35     11          47
1:V2R3RB      TABLE01                    32     19          98

what this says is that if I was to pack just these 2 tables I could recover 30 of the 145 cylinders these 2 tables occupy and packdisk would only have to scan 145 cylinders to complete rather than having to scan the whole system.

Using showfsp and scope table allows packdisk to be a lot more efficient, in this example we could recovering 20% of the cylinders packdisk scans.

Here is how you use the list to run a "PACK TABLE" on just the specified tables.

scope table "Crashdumps.Crash_20010223_155740_09" 0
packdisk fsp = 15

scope table "V2R3RB.TABLE01" 0
packdisk fsp = 15

Now granted your tables would be much bigger than my example tables here, but the concept is the same.

If recoverable Cylinders is negative it means that this table would actually be UNPACKED to the desired fsp if you ran a full system packdisk and therefore occupy that many more cylinders once the packdisk completes.

Showfsp has other options which allow you to tailor the list to your preferences like.

      only examine tables > 200 cylinders
             ( -c 200 )

      only display tables where we can reclaim more than 20 cylinders.
             ( -r 20 )

-a   Show all tables bigger than -c  regardless
          of -m or -d

-c    Minimum table size (default 2 )
          packdisk can't pack a 1 cylinder table.

-r     Minimum Cylinders recovered. (default 1 )
          Packdisk will only recover full cylinders

-d      Desired FSP after Packing.
         Default - behave like packdisk when user doesn't specify an FSP=

                   Use TLA FSP for tables if it exists
                   Use System wide FSP (from dbscontrol ) if not.

-m     Minimum FSP before packing. (default 0 )


     
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