AIX中调整VMM(国外英文资料).docVIP

AIX中调整VMM(国外英文资料) AIX VMM adjustment 1. For the DB2 database (including INFORMIX) systems, in many cases, the database files cache, there is no need in the operating system level and then to the file cache. This makes it necessary to limit the amount of memory the operating system is used for file cache, so that the DB2 (INFORMIX) database system can use more physical memory. This feature can be done by setting the AIX VMM (virtual memory manager) parameter. Four related parameters are described below. Maxfree: the maximum number of free memory lists (freelist) in the VMM. Minfree: the minimum value of the free memory list (freelist) in the VMM. Maxperm: the maximum percentage of physical memory that is allowed to be cached. Minperm: setting the allowed file cache accounts for the smallest percentage of physical memory. In AIX virtual memory manager always maintain a list of free memory, if memory memory less than minfree specified in the list of values, the VMM will start page, stealer, steal from already allocated memory memory is added to the list of free memory, put the content in the page Space. If the free memory list exceeds the value specified by maxfree, then page stealer stops the memory theft. So in the real system, if the free list of memory is always greater than or equal to the value set by maxfree, there should be no memory shortage in the system. When page stealer is working, it checks the minperm and maxperm value is set, if the value of the current file cache is less than the minperm set, then it will be calculated at the same time from the file system cache and memory to steal pages. When the file cache is greater than the value set by maxperm, it will only steal the page from the file system cache. When the file is in between the two, it will steal the page from the file system cache unless the file cache repages is larger than the calculated cache. Operating system default maxperm value is 80, for the database system, should set the value of a