Sybase 12.4.2 manual Avoiding buffer manager thrashing, 476

Avoiding buffer manager thrashing

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Example of -threadsThe results of the -threadsoption look like the following: option

Options string for Main cache: "-threads -file_suffix threads-iqmon -append -interval 10"

Threads

2000-01-24 10:59:24

CPUs	Limit NTeams MaxTms NThrds				Resrvd Free		Locks Waits
10	100	4	12	100	13	68	106	590
10	100	6	12	100	12	63	4	6
10	100	6	12	100	12	63	0	0
10	100	7	12	100	12	62	1	1
10	100	7	12	100	12	62	0	0
10	100	7	12	100	12	58	1	5
10	100	7	12	100	12	58	0	0

Avoiding buffer manager thrashing

Operating system paging affects queries that need buffers which exceed the free memory available. Some of this paging is necessary, especially as you allocate more and more physical memory to your buffer caches. However, if you overallocate the physical memory to your buffer caches, the operating system paging occurs much more frequently, and it can cause your entire system to thrash. The reverse is true as well: IQ thrashes if you do not allocate enough memory to your buffer caches.

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