System Backups
In this article, I would like to discuss system backups. Why do you perform a system backup? While there are many valid answers, the most common ones are: for recovery in the event of disk failure(s): or to recover files that are accidentally purged or “damaged” by jobs that do not run as expected. Here are some tips and answers to frequently asked questions concerning system backups.
Logical Issues
What files should I back up? Are you backing up files that never change such as archive databases? Not only is this a waste of time, but it increases the amount of data that must be skipped to restore a file that occurs later in the backup. What order are you backing up the files? If you are backing up to a DDS tape drive that does not support fast search capability, the order in which you backup files can greatly reduce the amount of time it takes to restore a given file. For example, if you frequently restore files in the PROD account you may want to change your backup command to:
STORE @.DATA.PROD,@.@.@-@.@.PROD;*T;SHOW=OFFLINE;PROGRESS
to put the files from DATA. PROD at the front of the tape.
Are you backing up large numbers of small files? It takes much longer to process many small files than is required to store one large file of equal amounts of disk space. By purging your system log files on a regular basis (LOG####.PUB.SYS and NMLG####.PUB.SYS), using a compression utility (such as SQUISHER or UHAUL) on your source files to reduce them into one large file, and keeping your documentation files offline and restoring only when needed, you can reduce the number of files you are storing. Do you print out a listing of the files stored? Do you review it?
Extremely important: Did you archive a year end full backup? I recommend a full system backup, a SLT, and listing be archived and stored offsite at year’s end. You should also archive a monthly full system backup.
Physical Issues
How are you storing your backups? Be sure they stored away from electromagnetic forces (motors, fans, etc.) and preferably in an environment with controlled temperature and humidity Do you keep any of your backup tapes offsite? You have to weigh the importance of accessibility to you backup as to how often and when to move your tapes offsite.
Do not take your backup home with you? This is an all too common method of storing offsite backups because of the ease of transporting a DAT tape in a pocket/briefcase/purse. However I cannot stress enough the importance of NOT doing this. Taking your backup home implies a certain amount of PERSONAL liability. If the backup media proves to be defective you can be held personally accountable if you have taken the responsibility of caring for it.
Use the write disable mechanism of your media to write protect your backup from being accidentally overwritten. Label and log your backup tapes. Keeping a log of who, what, when and how long, and properly labelled tapes will save many headaches when it comes time to restore a file. Furthermore, with a log you can determine that a backup that normally takes one and one half hours completes in 50 minutes is a clear indication that your backup is not likely to be complete.
These and many other issues vary from site to site. My point is that if a backup is worth doing, it is worth doing right