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Home -> Community -> Usenet -> c.d.o.server -> Re: Shared Pool Components
Hello,
The SGA is made up of a header and four portions as shown by v$sga. The header size is platform specific, but 8K is normal. Each of the four main portions is rounded up in size to a memory page (4K on most Unix systems). You can use 'ipcs -mb' on Unix to check this.
The size of the variable portion is approximately the shared_pool_size less the size of the buffer cache hash chain structure plus the size of the other fixed permanent memory objects such as the process and session tables and so on. It is this computed size that is reported in v$sga and v$sgastat, although the extra memory included from rounding up to a memory page boundary is actually used as part of the shared pool. You can confirm this by checking the sum of the sizes of the memory chunks in x$ksmsp. Note that there is a small overhead for the memory segment header.
I would suggest that you not attempt to reconcile the data in v$sgastat with your shared_pool_size parameter value. It does not reflect the rounding up, and I beileve that the sizes of the dynamic allocations are fudged anyway. I've never been able to reconcile it with x$ksmsp or memory heap dumps, in which I have much greater confidence.
Regards,
Steve Adams
steveadams_at_acslink.net.au
>What components make up the Shared Pool? Selecting from v$sgastat gives
>all SGA components - which ones add up to the number of bytes specified in
>the SHARED_POOL_SIZE parameter?
>
>Thanks !!!
Received on Tue Feb 03 1998 - 00:00:00 CST
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