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author's profile photo Former Member
Former Member

Two reason for swap

Please refer to following contents first:


Swap occur for two reason: enough free space left in the buffer for buffering the new object

2.the buffer has run out of free directory entries.

Directory entires determine how many different objects can be contained in one buffer area.


Here is my thought:

1. One work process has own buffer area in local memory.

2. In work process's buffer area, there are some directory entires to store different objects.

3. I think the directory entires is object group, each object has own directory entries, and can not be placed into another directory entries.

4. There are some directory entires in one work process's own buffer area in local memory

5. If we define too many directory entires in work process's own buffer, the actual size for each directory entries is cut down.

I am not sure my thought is right. For the first reason of swap, does it mean there is no free space in one directory entires?

Please advise. Thanks so much.


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    author's profile photo Former Member
    Former Member
    Posted on Jun 09, 2008 at 02:39 PM


    Check below link. It gives how to tune buffer.



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    • Former Member Former Member

      Hi James,

      Buffer consist of 1) the data part and 2)administrative data.

      Lets consider short nametab buffer for example,

      Profile parameter rsdb/ntab/sntabsize ajusts the size of the data part of the short nametab buffer.

      There is an other part of the buffer holding administrative data. The size of this administrative part depends on the platform (for instance for 64bit systems more space is needed than for 32bit systems) and on profile parameter rsdb/ntab/entrycount(i.e Dir. size Entries). Each Directory entries consumes about 300Bytes of data. You can do the calculation now!

      For differend sizes of parameter rsdb/ntab/sntabsize the size of the administrative part should be the same, unless you incease rsdb/ntab/entrycount.

      To check the current sizes, you can use transaction AL12, menu path

      Statistics->Buffers->STAB buffer->Overview

  • author's profile photo Former Member
    Former Member
    Posted on Jun 09, 2008 at 02:30 PM

    Is there anyone who can answer my question? Actually I don't understand what is directory entires in buffer.

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