Backing up the message log file dbname.iqmsg and the message log archives is a good idea, even though these files are not required for a restore.
If problems occur during a restore, the .iqmsg file contains information that proves that the database was shut down before the backup started. The message log files may be useful in diagnosing the cause of the database failure from which you are recovering. Be sure to make a copy before restoring, for use in later analysis.
If IQ message log wrapping is enabled (the IQMsgMaxSize server option or the -iqmsgsz server startup switch is not equal to zero, and IQMsgNumFiles server option or the -iqmsgnum server startup switch is zero), you will probably want to back up the .iqmsg file so that all messages are accessible in the event you need them for diagnostic purposes.
If message log archiving is enabled (the IQMsgMaxSize server option or the -iqmsgsz server startup switch is not equal to zero and the IQMsgNumFiles or the -iqmsgnum server startup switch is not equal to zero), the server automatically backs up the message log archives. The maximum amount of message log that is archived is 128GB, which is sufficient in most cases.
Backing up the message log archives is required
before a server restart. After the server restarts, the existing
log archives are ignored and a new archive is created when the dbname.iqmsg file
is full. To preserve the old archive logs, back up the files before
restarting the server.
