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The amount of paging that gets done is totally independant of the paging space available. OTOH, disk is cheap, so why not? Some paging is nearly inevitable, but not undesirable. A lot or incessant paging indicates that you need more RAM.
It will put your entire data set into RAM if you access it all, and leave it there until it needs the memory pages to keep above minfree. When you start to see page ins is when you can start to worry.
I just wanted to hear what you guys would say to this. It really depends on your application and how youve configured memory usage in AIX. If its configured for early allocation then one page of page space will be allocated to each page of real memory as soon as its addressed. No Account? Jose Finger Jose Finger 1 1 1 bronze badge. Was there supposed to be something in the quote box there? That memory is fully used is a "good thing". Memory is designed to be used. ImHere ImHere 37k 3 3 gold badges 73 73 silver badges bronze badges.
Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. Now live: A fully responsive profile. Related 3. Constant and excessive paging indicates that the real memory is over-committed.
In general, you should:. Avoid constant paging unless the system is equipped with very fast expanded storage that makes paging between memory and expanded storage much faster than Oracle Database can read and write data between the SGA and disks. Allocate limited memory resource to where it is most beneficial to system performance. It is sometimes a recursive process of balancing the memory resource requirements and trade-offs.
If memory is not adequate, then build a prioritized list of memory-requiring processes and elements of the system. Assign memory to where the performance gains are the greatest. A prioritized list may look like the following:. For example, suppose you query Oracle Database dynamic performance tables and views and find that both the shared pool and database buffer cache require more memory.
Then, assigning the limited spare memory to the shared pool may be more beneficial than assigning it to the database block buffer caches. You can configure Oracle Database block size for better Input-Output throughput. For databases on raw partitions, Oracle Database block size is a multiple of the operating system physical block size bytes on AIX.
Oracle recommends smaller Oracle Database block sizes 2 KB or 4 KB for online transaction processing or mixed workload environments and larger block sizes 8 KB, 16 KB, or 32 KB for decision support system workload environments. By increasing the number of buffers, you can maximize CPU usage, and by doing this, increase overall throughput.
The performance gains depend on CPU usage and the degree of parallelism that you use when loading data. The BUFFER parameter for the Import utility should be set to a large value to optimize the performance of high-speed networks when they are used. Disk Input-Output contention can result from poor memory management with subsequent paging and swapping , or poor distribution of tablespaces and files across disks.
Ensure that the Input-Output activity is distributed evenly across multiple disk drives by using AIX utilities such as filemon , sar , iostat , and other performance tools to identify disks with high Input-Output activity. The primary objective of striping is to achieve high performance when reading and writing large sequential files. Effective use of the striping features in the Logical Volume Manager enables you to spread Input-Output more evenly across disks, resulting in better overall performance.
When you define a striped logical volume, you must specify the items listed in the following table:. Performance gains from effective use of the Logical Volume Manager can vary greatly, depending on the Logical Volume Manager you use and the characteristics of the workload. For decision support system workloads, you can see substantial improvement. For online transaction processing-type or mixed workloads, you can expect significant performance gains.
Address the following considerations when deciding whether to use journaled file systems or raw logical volumes:. File systems require some additional configuration AIX minservers and maxservers parameter and add a small CPU overhead because Asynchronous Input-Output on file systems is serviced outside the kernel. Different vendors implement the file system layer in different ways to capitalize on the strengths of different disks.
This makes it difficult to compare file systems across platforms. The introduction of more powerful Logical Volume Manager interfaces substantially reduces the tasks of configuring and backing up logical disks based on raw logical volumes. In earlier versions of AIX, file systems supported only buffered read and write and added extra contention because of imperfect inode locking.
File System Options. Direct Input-Output and Concurrent Input-Output support enables database files to exist on file systems while bypassing the operating system buffer cache and removing inode locking operations that are redundant with the features provided by Oracle Database.
The following table lists file systems available on AIX and the recommended setting:. Therefore, the Oracle home directory and data files had to be placed in separate file systems for optimal performance. The Oracle home directory was placed on a file system mounted with default options, with the data files and logs on file systems mounted using the dio or cio options. Because the directIO setting disables asynchronous Input-Output it should normally not be used.
As mentioned earlier, you should still place Oracle Database logs on a separate JFS2 file system for optimal performance. If you are using GPFS, then you can use the same file system for all purposes.
This includes using it for the Oracle home directory and for storing data files and logs. To move from a journaled file system to raw devices without having to manually reload all the data, perform the following steps as the root user:.
Create a raw device preferably, in a BigVG using the new raw logical volume device type -T O , which enables putting the first Oracle block at offset zero for optimal performance:. Use dd to convert and copy the contents of the JFS file to the new raw device as follows:. The first Oracle block on a raw logical volume is not necessarily at offset zero.
However, the first Oracle block on a file system is always at offset zero. When you have determined the offset, you can copy over data from a raw logical volume to a file system using the dd command and skipping the offset. The following example assumes an offset of bytes:. You can instruct Oracle Database to use many blocks smaller than the maximum capacity of a raw logical volume.
If you do this, then you must add a count clause to ensure that only data that contains Oracle blocks is copied. The following example assumes an offset of bytes, an Oracle block size of 8 KB, and blocks:.
Oracle Database takes full advantage of asynchronous Input-Output provided by AIX, resulting in faster database access.
When using asynchronous Input-Output on file systems, the kernel database processes aioserver control each request from the time a request is taken off the queue to the time it is completed. The number of aioserver servers determines the number of asynchronous Input-Output requests that can be processed in the system concurrently. So, it is important to tune the number of aioserver processes when using file systems to store Oracle Database data files.
Use one of the following commands to set the number of servers. This applies only when using asynchronous Input-Output on file systems:. The man pages for more information about the smit aio and chdev commands.
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