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Configuring wash size of a buffer pool

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Dear Experts,

 

 

Acc to http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc31644.1550/html/sag2/CHDGHFEG.htm

which states " if you configure a 16K pool with 1MB of space, the pool has 64 buffers; 20 percent of 64 is 12.8. This is rounded down to 12 buffers, or 192K, is the size of the block that is allocated to the wash area",

 

I think that wash size of our 16K memory pool is not rightly configured.

 

Cache: default data cache,   Status: Active,   Type: Default
      Config Size: 33792.00 Mb,   Run Size: 33791.97 Mb
      Config Replacement: strict LRU,   Run Replacement: strict LRU
      Config Partition:           16,   Run Partition:           16
IO Size  Wash Size    Config Size  Run Size     APF Percent
-------- ------------- ------------ ------------ -----------
    16 Kb    2293760 Kb 22937.50 Mb  22937.47 Mb     10
   128 Kb     573440 Kb 10854.40 Mb  10854.00 Mb     10

 

Based on Sybase manual, calculaion is, 16K pool with 22937 MB of space, the pool has (22937*1024)/16 = 1467968 buffers; 20 percent of 1467968 is 293593.6. This is rounded down to 293593 buffers, or (293593*16K) 4.47 GB, is the size of the block that is allocated to the wash area.

 

Similarly, fior 128K memory pool, it comes to 2.1GB.

 

Am i right in calculating the wash size (here)?

 

or

In real time, do  I need condsider any other thing in order to conclude near perfect value for the wash size of 16k and 128k memory pools?

 

Environment:

ASE 15.7 SP122 on AIX 7.1 in an OLTP+ OLAP combined environment

 

Regards,

Rajesh


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