Alarm Persistence

Real-time records are stored in memory. As such, the values are cleared when the service is stopped. However, it may be desirable to persist the values so that they are available to the service upon restart. This is called data persistence. The CAS can be configured to persist alarms and the queue of alarm history records.

CasPersist.dat

The CasPersist.dat file retains all current alarms in the CAS. When the CAS shuts down and starts up again, the CAS will restore all alarms that were in the CAS at shut down. This file is periodically saved while the service is running. The default rate is every 10 minutes; however, you can change the period in the CAS configuration file by specifying the PERSIST_FILE_REFRESH_RATE keyword.

AlmHistPersist.dat

The AlmHistPersist.dat is the queue of records that are waiting to be sent to the Alarm Event Logging Service (ELSALM). The AlmHistPersist.dat file is the CAS Alarm history and when the CAS shuts down and starts up again, alarm history records are not lost. The AlmHistPersist.bak is a backup of the last persisted file, so before a new file is written, the old one is saved. Back up the AlmHistPersist file only when the service is not running.