Re: shared_pool_size v/s large_pool_size

Since you are using MTS, you will want to use the Large Pool. To understand why, a quick tutorial on MTS might be in order.

When a user connects, they create a server process (in Unix). That server process is basically responsible for performing two tasks. One is to read data from disk. The other task is to allocate space in memory for the user to perform in-memory sort operations. This amount of space is determined by the SORT_AREA_SIZE parameter. If there are many users connected to the system, then the total amount of system memory allocated due to the high number of users can place a harsh burden on system resources. To address this issue, Oracle created MTS in Oracle 7.

For MTS in Oracle 7, the two tasks mentioned above are split. The server process is now shared by multiple connections. The server process is still responsible for reading data from disk. This process will now read data for multiple users. The second task is now performed in the SGA, more specifically the Shared Pool. Too many users can hog up space in the Shared Pool when running MTS. If you are running MTS in Oracle 7, you will need to greatly increase the size of the Shared Pool. Unfortunately, by hogging up the Shared Pool, other things like the Data Dictionary Cache and the Library Cache could not get enough room.

Oracle addressed this issue in Oracle 8. Beginning with Oracle 8, you can now allocate a Large Pool. This lets MTS perform the second task mentioned above in the Large Pool, not the Shared Pool. This frees up the Shared Pool for things that it was designed for (Library Cache & Dictionary Cache). User's sort operations are now performed in the Large Pool and do not interfere with the Shared Pool. But this will only happen if you define the Large Pool. If you do not define the Large Pool and you still run MTS, then the Shared Pool will be used.

HTH,
Brian

Gunjeet Singh wrote:
>
> Hi,
>
> Could someone please explain the use of the new Oracle8 init parameter
> "large_pool_size" ? How is it related to
> shared_pool_size ?
>
> We are using MTS mode for Oracle 8.1.6.
>
> Thanks,
>
> Gunjeet
 

-- 
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Brian Peasland
Raytheons Systems at
  USGS EROS Data Center
These opinions are my own and do not
necessarily reflect the opinions of my 
company!
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