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Jeff Quade ([log in to unmask]) wrote:
 
: We're installing 5.0 of MPE/iX. In reviewing the "backdate" process,
: it appears that if you want to back off of 5.0, you must reinstall
: 4.0. Is there no simpler way, like renaming files and rebooting? Or
: rebooting from a different LDEV? We are a bunch of IBM Mainframe support
: personnel who've been given an HP 3000 to support and we don't have a
: firm grasp on MPE yet. Any help will be GREATLY appreciated.
 
#Steve Elmer Software Engineer - HP - CSY wrote :
 
#There is no "simpler" way to backdate.  The backdate instructions exist to
#assist you in accomplishing a backdate should it become necessary.  It is
#not really a recommended operation.
 
#The reason the backdate process is necessary is that the update from 4.0
#to 5.0 made some significant changes to your system.  Simply purging a few
#files will definitely _not_ allow you to run 4.0 again.  If you attempt
#this, you can expect to have serious problems on your "4.0" system and
#may even end up requiring a reload.
 
I  endorse this. I built a 'dual-boot' system which had two sets of separate
system volume
set disks , either of which could _only_ be accessed at system boot time.
The 5.0 install went fine , the user volume sets containing my data were brought
on-line without any problems.
I shutdown the system and booted from my 4.0 system volume set and the system
failed as it tried to mount the user volume sets. This was because the 5.0
install/update
had converted various control data structures (e.g. VSIT, TXM logs etc) to a
format which
is not backward compatible with 4.0 and it had not told me of this. My solution
was to
reboot the 4.0 disks with the private volumes (old MPE V terminology dies hard)
switched off. When MPE/iX 4.0 came up I powered up the 'converted' PV's and
scratched
each volume!
 
#If you think the backdate process is too onerous, you haven't had to do
#a reload recently...
 
This statement is being economical with the truth ; to go backwards from 5.0 to
4.0
you must re-install MPE and AL your data ( in my case 200Gb on the Dev
system)!!!
 
 
#Please, please follow the backdate process if you must backdate!
 
You have been warned,
 
 
Tony Rendell
 
 
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