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Swap space usage 1
- Thread starter nassrin5
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sybaseguru
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nassrin5,
You have to understansd that large applications such as Oracle tend to have processes with large virtual address spaces. This is typically the result of attaching to large shared memory segments used by Oracle and large copy-on-write (COW) segments that get mapped but sometimes never actually get touched. The net effect of this is that on this host supporting multiple Oracle instances, the virtual address space requirements will grow to be quite large, typically exceeding the physical memory size of 8GB in this case. Consequently, we will require a fair amount of swap disk configured to support these multiple Oracle instances with large Virtual Address space running concurrently. As a result we will need to configure between 1 or 1.5 times the amount of max shared memory for swap so Oracle processes can fully utilize all of the physical memory without running out of virtual swap space. In addition, UGA may require swap space. If the user process runs out of sort area in memory, it will start using the user temporary tablespace. If that allocation runs out too, the process will start using the swap area which is effectively disk space resulting in severe performance problems for Oracle
You have to understansd that large applications such as Oracle tend to have processes with large virtual address spaces. This is typically the result of attaching to large shared memory segments used by Oracle and large copy-on-write (COW) segments that get mapped but sometimes never actually get touched. The net effect of this is that on this host supporting multiple Oracle instances, the virtual address space requirements will grow to be quite large, typically exceeding the physical memory size of 8GB in this case. Consequently, we will require a fair amount of swap disk configured to support these multiple Oracle instances with large Virtual Address space running concurrently. As a result we will need to configure between 1 or 1.5 times the amount of max shared memory for swap so Oracle processes can fully utilize all of the physical memory without running out of virtual swap space. In addition, UGA may require swap space. If the user process runs out of sort area in memory, it will start using the user temporary tablespace. If that allocation runs out too, the process will start using the swap area which is effectively disk space resulting in severe performance problems for Oracle
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