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Shared Memory Parameters?

Posted in 2000

Topics: Storage & Space Management, Server Administration

Calvin Shoults — — source: Informix-list mailing list archive (1991-1998)

I am working with an existing database that has some onconfig parameters that I am questioning. One of our problems is extents, but another reason we get hammered during the day might be the following shm parameters. OL Engine Vers. 7.31 on HP 9000 Aprx. 400-600 users Database - 14 gig 6 - CPUS 21 chunks used for database # Locks - 200,000 # Buffers - 300,000 # NUMAIOVPS - 56 # PHYSBUFF - 1024 # LOGBUFF - 128 # LOGMAX - 50 # CLEANERS - 22 # SHMVIRTSIZE - 1,400,000 # SHMADD - 131,072 # SHMTOTAL - 0 # LRUS - 56 # LRU_MAX_DIRTY - 5 # LRU_MIN_DIRTY - 2 # STACKSIZE - 32 I am considering changing to # Buffers - 2,000 # LRUS - 50 # LRU_MAX_DIRTY - 60 # LRU_MIN_DIRTY - 50 # CLEANERS - 8 Any thoughts would be appreciated.

↪ replying to Calvin Shoults
Carlson@WHSmith — — source: Informix-list mailing list archive (1991-1998)

Calvin Shoults wrote: > > I am working with an existing database that has some onconfig parameters > that I am questioning. > > One of our problems is extents, but another reason we get hammered during > the day might be the following shm parameters. > > OL Engine Vers. 7.31 on HP 9000 > Aprx. 400-600 users > Database - 14 gig > 6 - CPUS > 21 chunks used for database > > # Locks - 200,000 > # Buffers - 300,000 > # NUMAIOVPS - 56 > # PHYSBUFF - 1024 > # LOGBUFF - 128 > # LOGMAX - 50 > # CLEANERS - 22 > # SHMVIRTSIZE - 1,400,000 > # SHMADD - 131,072 > # SHMTOTAL - 0 > # LRUS - 56 > # LRU_MAX_DIRTY - 5 > # LRU_MIN_DIRTY - 2 > # STACKSIZE - 32 > > I am considering changing to > > # Buffers - 2,000 Why? With that many users on the system, actively hitting the instance? Only way I'd consider dropping BUFFERS is if UNIX was paging to disk. But then, I wouldn't drop it that much. > # LRUS - 50 > # LRU_MAX_DIRTY - 60 > # LRU_MIN_DIRTY - 50 Depending on how dirty your pages get (updates, etc.) and how slow your disks are, you might increase your checkpoint duration. I'd keep 'em low. > # CLEANERS - 8 Cleaners should equal LRUs. I'm curious: what performance issues are you seeing? -- John Carlson Informix DBA WHSmith USA #include std_disclaimer.h /* These are my opinions, not my company's opinion */

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