Issue:
Server Availability Index (SAI) is low on systems where memory, processor, and network are all reported as plentiful. (e.g. 1-15% processor peak, 20% network interface(s) peak, and "plentiful" memory).
Availability Index goes down to 0. Users may or may not see access issues. In addition, cluster failover doesn't occur (fails) since both machines are reporting 0 availability index.
Solution:
Adjust the "Server_Transinfo_Range" from the default 6 to something higher (e.g. 8 or 10). Starting in Domino 6.5 and Domino 6.04, the documentation was improved with more information on these settings. See "Server Availability Index" in index of Domino Admin 7 Help (or higher).
Notes:
The command sh ai will help you determine the proper values. I generally go one or two under the value unless I am really sure it's experiencing the maximum load.
A higher Server_Transinfo_Range value means a higher availability index (than 0 hopefully) when the server is under a decent load, and 0 when near or at it's peak/heavy load that would cause concern.
e.g. Server_Transinfo_Range=25
This expansion factor for the STR, is a 2 raised to the power entered, which, for 25, is 33,554,432.
Remember that a server also has to handle requests that fail-over from another server in an outage, take this load into consideration when both planning your servers as well as for this index for what is truly a heavy/max load.
In VMs we are noticing some really low latency and high latency times with requests being fulfilled. The following notes.ini, R8.x and higher, parameters can be used to take out the extremes for a more even calculations. The values are in micro seconds. So the following has a 2 ms minimum.
Server_MinPossibleTransTime=2000
Server_MaxPossibleTransTime=20000000
I've never needed to update the collection period, but below are those two notes.ini settings.
Server_Transinfo_Max = x, where x is the number of collection periods
Server_Transinfo_Update_Interval = y, where y is the length of each period between collections.
Console commands:
Show the calculation matrix:
> sh ai
Show the expansion factor:
> sh stat server.expansionfactor
Show availability index:
> sh server
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