Oracle 9i Performance tuning on AIX

Products: AIX, Oracle

Platform: pseries, AIX

Version: All

Conflicts in memory access now when the process requests more memory than the total physical memory of the system, in order to handle this situation, the system swaps the program and the data between the memory and the hard disk.

Control Memory Exchange operation (paging)

A large number of memory exchange operations can greatly affect the performance of the system, especially when the database files are created on the file system (JFS and JFS2). In this case, the data that is frequently accessed is present in the SGA as well as in the file cache. This same data cache two times in memory, will reduce the use of memory efficiency, so that the memory of frequent exchange operations, resulting in the system I/O bottleneck, reduce the performance of the entire system.

Adjust the file cache on AIX

On AIX, you can adjust the system file cache to control memory exchange operations by adjusting the minperm and maxperm parameters in the Vmtune command, and the adjustment of minperm and Maxperm parameters should follow the following guidelines:

The memory paging algorithm swaps both the file cache page and the program page (computational pages) when the memory file cache page is below minperm.

When a file cache page in memory is above maxperm, the memory paging algorithm only swaps the file cache pages.

The memory page Exchange algorithm typically swaps only file cache pages when the cached page in memory is between Minperm and Maxperm, but the program page is also swapped if the exchange rate of the file cache pages is greater than the program page.

Default values for Minperm and Maxperm parameters:

MINPERM = ((number of memory page) - 1024)*0.2
　　MAXPERM = ((number of memory page) - 1024)*0.8

You can set the Minperm to 5% memory pages with the following command, while the maxperm is set to 20% of the memory page.

# vmtune-p 5-p 20

The default values are 20% and 80%, respectively.

In an Oracle database application environment, Minperm and Maxperm can be set to 5% and 20%, or even smaller, to allow more memory to be used for Oracle's SGA rather than for the system's file cache.

Configure enough swap areas

If the swap space is insufficient, the system response slows down or hangs, and the size of the swap area depends on the size of the system memory and the application's memory requirements. You can dynamically increase the swap area on AIX, or you can use the LSPs command to view the usage of the swap area and use Vmstat to monitor the operation of the system memory page Exchange.

Typically, the size of the swap area needs to be larger than the actual memory of the system, depending on the memory requirements of the application. Users need to monitor the usage of the swap area and increase the space of the swap area as needed. A larger swap space may be required for running Oracle Application or Oracle development tools.