Communicator 3000 MPE/iX Release 6.0 (Platform Software Release C.60.00) (30216-90269)

218 Chapter 10
Technical Articles
Transaction Manager
Backdating the OS
You can backdate the OS to an earlier version with the system log in
the expanded state. The only condition is that the residual logs also
must have been expanded or truncated to match it before the
backdating is done. That would mean a complete, proper recovery of the
volume set in question has to be done before the backdate operation.
Warnings
The expansion of the system log or the residual logs may fail due to one
or more reasons. In that case, the system will report it through a
warning message (in reverse video) on the console.
If it fails due to lack of disk space, make sure that there is sufficient
contiguous space on the master that would fit the need for the
increment in the system log size. Then reboot the system so as to enable
it to complete the task of matching the sizes of residual logs with that of
XM system log.
Transaction Copy-forward
The Copy-Forward solution eliminates the frequent occurrence of SA
2200 by copying forward the activity records of slow system
transactions into the next log half and continuing logging in the current
log half.
This is an enhancement to FOS and there is no user interface needed to
make this available.
Additional System Requirements
To accomplish the task of copying forward the slow transactions, a new
system file called the copyfwd buffer is created on the master of each
volume set. This is done at the time of creating the volume set or at the
first time of booting the system with this version of MPE/iX.
The size of this new buffer is half of the XM system log (which is about
12 MBytes).
When It is Activated
When the XM logger sees slow system transactions at the time of
wrapping back to the start of the circular XM system log file, it
activates this solution to copy forward all such slow transactions first
into the copyfwd buffer, sorts them and then continues with logging of
the current transaction. This copying forward is done on such slow
transactions for a certain number of times (about 100 times, as of now),
and then, if they are not over even then, it would issue SA 2200,
concluding that there is something that can put the system in jeopardy.