On Thu, 15 Mar 2007 09:42:51 -0500 McKown, John said: >This is not important, but I just have to ask this. Does anybody know >why the original designers of VM did not do something for "minidisks" >akin to a OS/360 VTOC? Actually, it would be more akin to a "partition >table" on a PC disk. It just seems that it would be easier to maintain >if there was "something" on the physical disk which contained >information about the minidisks on it. Perhaps with information such as: >start cylinder, end cylinder, owning guest, read password, etc. CP owned >volumes have an "allocation map", this seems to me to be an extention of >that concept. >Just curious.
Just a guess. The CP Directory has information for each user. At logon time, the information about a single user is available very quickly. If the information about how a disk was divided into minidisks was stored in a "VTOC", do you remove it from the Directory, or do you keep the information in two places? (Since there is a small VTOC on CP volumes, it really could have been in the VTOC, probably with different DSCB formats) If you remove it from the directory, then you greatly slow down logon processesing, and lead to situations where if a volume is offline, the system would not know that something was missing for the user. If you keep it both places, which is the authoritative source? I'd have to check the history, but I bet that the source Directory was kept by hand originally, in a flat file, leading to even more difficulties is keeping them in sync. >-- >John McKown >Senior Systems Programmer /ahw
