The collection of history may require consideration before activation on older platforms or systems short of disk space.
History files (HSTxxDB) are simple Enscribe keyed sequence files with a single primary key. No alternate keys are used and the files are not TMF audited. If necessary, history files may be purged. Stop MOMI, purge the desired files (or purge data) and restart MOMI. MOMI automatically creates files if needed. No special recovery procedures are required.
The activation of history primarily 1) will consume disk space, and 2) increase the I/O load to the disk volume(s) where MOMI history files reside. Additionally, older processors prior to the S72000 may notice a slight increase in CPU utilization. However, disk space and I/O load is really the primary considerations.
The default amount of disk space consumed by MOMI history files may be found in Resizing History Files. Care should be given to not impact disk space required by other applications.
MOMI initially writes history to the HST01DB file. History is consolidated from HST01DB into HST02DB, from HST02DB into HST03DB and finally from HST03DB into HST04DB. The consolidation process generally a) reads all needed records from one file, b) writes all needed records into the second file and c) goes back and deletes oldest eligible data from the first file. Spreading MOMI history files out across multiple disk does not really 'help' to provide any performance improvements at least to MOMI, however it may help other applications also residing on the same volume if it is heavily loaded.
History is written to HST01DB every few minutes by default. All MOMI history is compressed and consolidated to help avoid unnecessary I/O. Consolidation into the other files occur at their history dump interval (default history dump intervals are found in HSTnnDB-HISTORY-DUMP).
Older or smaller powered processors, such as the S7000, may see an increase of one to two percent in CPU utilization. Processors such as the S72000 and beyond would hardly report any difference.