Communicator e3000 MPE/iX Release 6.5 (Non-Platform Software Release C.65.00 (30216-90291)

Chapter 5 127
Internet and Interoperability
Large Transactions for IMAGE Users
Solution Objective
The main objective of this solution therefore has been to increase the transaction size from
the existing 4 MB. The second objective is to increase the size of the XM userlog from the
current value of 64 MB to support large transactions.The third objective is to ensure
compatibility with existing applications, so that they can run without any problems even
with these enhancements.
Overview of the Solution
In order to achieve the above mentioned objectives, the capabilities of the following
products /subsystems of MPE/iX have been enhanced:
• Transaction Manager
• TurboImage/iX
• Image/SQL
• ALLBASE/SQL
Transaction Manager
A patch MPEKXG8 was released (on MPE/iX 5.5) to cater to the increase in number of
transactions by reducing the data stored in a transaction.
This was made possible, by keeping only the essential information required for possible
rollback in future. A large amount of internal data becomes irrelevant after completion of
an extended transaction (we will refer any dbput/ dbdelete/ dbupdate as an extended
transaction throughout this article). This allows for more transactions even within the
current 4 MB limit.
However, the long term solution addressed here, calls for increasing the transaction limit
to larger values. Based on current OS limits, the maximum transaction size has been
increased to 32 MB in this solution. In addition to this, XM has been changed to send out
an early warning message (soft limit warning), before the transaction size limit of 32 MB is
hit (i.e. at 28 MB). When, ultimately the transaction size reaches 32 MB, it aborts the
process and rollback the transaction.
Another enhancement in XM is to increase the userlog. The current userlog size is 64 MB
per volume set. Currently, for each transaction, the information that can be contained in
the userlog is limited to 4 MB. Due to the increase in the transaction size for each process
(to 32 MB), the total userlog file should also be increased. The userlog resides on the
master volume of a volume set. User can use VOLUTIL utility to increase the size of the
userlog (the default value is 64 MB) with the following,
>From VOLUTIL,
ALTUSERLOG <volset-name> <new size>
This command accepts the volume set name and the new size of XM userlog for it in
sectors. It can not be less than 264256 sectors corresponding to 64 MB. One caution is that
ldev 1 has limited reserved space and one can not expand the XM userlog beyond that.
The actual expansion of the XM userlog happens when user boots the system next time.
This is because the XM log files can not be expanded/truncated while in use.
During bootup, just after recovery of the userlog, the XM userlog is expanded and a