March 03, 2017
When and how to back up 3000 directories
Editor's Note: Homesteading Editor Gilles Schipper weighs in on using the 3000's store directory option, rather than invoking the buldacct program, to make clean backups.
By Gilles Schipper
It's common to see confusion surrounding the use of the ;directory store option versus the buldacct directory creation program. In order to benefit from the store ;directory option, one has to utilize the option almost perfectly in both the store and the restore following a system INSTALL. Consequently, it becomes much easier to fall back on the buldjob options to re-create the directory -- although that option is inferior.
In order to be able to effectively utilize the directory option, the first thing that must be done properly is to ensure that the appropriate ;onvs= option is also used in the case where user volumesets are utilized. Otherwise, the non-system volumeset directories do not get restored after the INSTALL since they are not on the tape.
But even if the store part is done correctly, the other opportunity to go wrong presents itself during the reload process.
The proper procedure during reload is as follows:
1. perform INSTALL
2. restore ;directory from tape
3. re-create disk and volumeset environment via VOLUTIL
Then -- and this where many go wrong,
4. Again restore ;directory from tape (this re-creates the volumset directory environment on the master volumes for all user volumesets for those utilizing it)
5. restore files
6. reboot with start norecovery (to enable network functionality)
Of course, for those that do not utilize user volumesets, the directory option becomes much less error-prone. And, for those that utilize third-party backup utilities, the ;directory option -- as utilized in the MPE store command -- is generally replaced with a similar option in the various backup utilities.The bottom line: for those that utilize the MPE store command to perform their backups, the properly-used ;DIRECTORY (and, if appropriate) corresponding ;ONVS= options) -- together with correct restore procedures as indicated above -- will get the desired result 100 percent of the time. Notwithstanding, of course, any tape issues occurring, which would be problematic no matter which directory re-creation option is used.
The bottom line is that the proper way to perform a full backup if you're using the MPE backup facility:
Of course, upon further reflection, and better than the store command: use sysgen to create a backup tape that not only contains all files, but also the SLT -- so that this one tape alone can be used to INSTALL and RELOAD your system. The use of sysgen for such purpose will require use of an indirect file.
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Early in the MPE/XL era, we got burned by not backing up with ;DIRECTORY, even after we implemented private volumes, which in turn required ;ONVS. We did know about ;ONVS but not about ;DIRECTORY.
As a result, after a system disk failure required a RELOAD, we learned that we had no directory structure on the private volumes.
From paper listings, I had to sit there and manually enter account and group names in private volumes, then rerun parts of the RESTORE to put files back on private volumes, and make enough room on MPE_XL_SYSTEM_VOLUME_SET for the o.s. to run!
Posted by: Tim | Mar 7, 2017 4:52:58 PM
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