|OLTP - Big Resident (buffers), small Virtual (SHMVIRTSIZE)|
|DSS - Small Resident, big Virtual|
|DSS may be up to 75% RAM if paging is not induced|
|DSS KEY FIELD|
|10 - 20% of SHMVIRTSIZE|
|can be used to make Informix more polite reserving resources for other applications. I have also had to use this when a failing malloc panics oninit|
Monitoring: -g seg One of the first things I check as consolidating shared memory segments can be huge bang for the buck.
Note that onmode -F (used to free memory segments) can cause system failures on an active system and should be avoided.
Sar -g 3 3 will show paging activity
To calc shared memory segments corresponding to a DB instance shmid 52564801*.0001 = SERVERNUM
|if > 0, will enhance parallelization of index builds (which after 7.2 are always parallel to some degree)|
|DSS should be 90% of SHMVIRTSIZE|
Quantum = (PDQPRIORITY/100)*(DS_TOTAL_MEMORY/DS_MAX_QUERIES)
Each sort thread gets quantum/#sort threads memory
A users effective priority = (pdqpriority/100) * ( MAX_PDQPRIORITY/100) where pdqpriority is set by the environment variable or the SET PDQPRIORITY statement.
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