Where do I start with the history parameters?
We recommend using the defaults. Remove comments or add the lines to the CONFMOMI file as referenced elsewhere in this document.
What if my file is not large enough? Will MOMI generate an error 45 (file is full) message?
If MOMI needs to write data to the history file and space is not available, some of the oldest data in the file is automatically deleted to make room for new. MOMI does not generate error 45 (file is full) messages nor error 43 (no disk space) for history files. This action occurs regardless of any other settings pertaining to how long data is retained.
Does dumping data more frequently cause MOMI to work harder?
Directly no, but indirectly yes. The information MOMI dumps to the history file has already been collected. Activation of history is the process of dumping this data to disk, allowing the PC Client to read the history data and maintain or delete old data from the history file. Therefore, no additional CPU cost is directly imposed in the collection process, just in what you do with the data after it is collected.
At what priority will the history be dumped to disk? Will it be high like MOMI (by default) is?
MOMI uses a server process, by default running at priority 95, to write data to disk. It does not write at the priority of $MOMI. MOMI uses three different servers to manage the history file. One server to write data, a second server to read data for PC Client requests, and a third server to delete or cleanup old data. See the CONFMOMI keyword documentation for additional information. Three keywords used to control the priority for access to the history file:
PRIORITY-DB-HST01DB - priority write
PRIORITY-DB-HSTxxDB-R - priority read
PRIORITY-DB-HSTxxDB-CON - priority delete/cleanup
What will happen if the server process that MOMI uses to write data to disk is bogged down or otherwise not able to get its data written out to disk?
MOMI will initially queue in memory the data waiting to be written to disk. This queue will continue for a period of time, before new data is discarded. Overall, MOMI will try to protect itself and your System by using more memory and discarding history data if necessary. In order to insure that all history data is collected, the MOMI server used to write data to disk should be given sufficient CPU so it will not normally be bogged down by batch or other long running programs.
I see a high CPU utilization of a MOMI process running at a low priority, and by using MOMI I tracked it down as performing large number of disk reads from a history file. What is going on?
Normally, that is normal. The PC Client has a great deal of flexibility in accessing the history data. The PC Client could be searching for a named process, reading data for display or perhaps performing a history export operation. MOMI protects your System by using a separate, configurable priority process to perform "bulk" history reads. If the default priority is too high for your System, lower the priority by using the keyword PRIORITY-DB-HSTxxDB-R .
I cannot find history records for a process?
To conserve disk space MOMI history records are written when a process 'changes' state or is active. If a process is active, inactive for a period of time, then active, there may be no history records for a portion of the inactive period of time. If you were to view all of the history records for this process, at the start of the inactive period of time there would be at least one record showing zero CPU busy, a gap in real time and then followed by a record showing activity. Activity is start/stop, CPU Busy, or other change in process state.