Announced in August 2007, IBM's mainframe operating system, z/OS 1.9, is now generally available. This release of the operating system has its share of large and small enhancements. What follows are the ones that caught my eye. If you want more information, I suggest reading the z/OS 1.9 Migration Guide in the z/OS Library Center.
Coupling Facility (CF)
RMF on z/OS 1.8 promises better and more extensive reporting on CF activity down to the structure level. This requires CF level 15 on a z9 server. With 1.9, CF management will be easier by putting your CF into "maintenance mode," making it ineligible for structure allocation just as if it were taken out of the preference list. Finally, there are some system duplexing performance enhancements that IBM hopes will speed up existing applications and enable duplexing for others where it was previously performance prohibitive.
System Management Facility (SMF)
This release allows you to write SMF data to the coupling facility, providing higher I/O rates, and enables the merging of several LPARs' data into one stream. An installation may also assign different log streams for different record types, all with different retention periods.
I'm sure a lot of the larger shops may appreciate the higher throughput with the coupling facility, but the separation of records typed into log streams is even more useful for those places that normally run without DB2 or MQ tracing due to the record volume. Now you can turn on these records and route them to different log streams where they can be managed separately.
And, if it turns out you don't need the data more than a couple of days, the records can be easily discarded while other SMF records are lapped up into daily, weekly and monthly processing.
More engine support
This is the first release to support 54 engines in one LPAR, including engines of all types: CP's, zIIP's and zAAP's. There is some virtual storage constraint relie
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f (VSCR) as Global Resource Serialization (GRS) has thrown some control blocks over the bar while the I/O Supervisor (IOS), Basic Control Program (BCP) and Network File Server (NFS) use more storage above the 16M line.
System Rexx
This release includes a new address space (AXR), allowing you to run Rexx outside of a TSO environment. Rexx has always been frighteningly powerful, but this is really scary because now Rexx scripts will be able to run authorized and/or from an operator command. This has the potential of executing some elaborate automation from a console or job stream without a package like SA OS/390.
Of course, it may be a little bit harder to exploit the promise of this facility given that Rexx programs usually load other interfaces (e.g., CPSM) to do what they need to do.
This release of z/OS also extends Rexx support to SDSF, helpful for automation in that it gives scripts the ability to read job and system log output.
VSAM
In case you're wondering, IBM modified the previous statement of direction concerning cluster attributes IMBED, REPLICATE and KEYRANGE. IBM decided to keep KEYRANGE. REPLICATE and IMBED, however, are still on the outs, although there's no firm date. IBM does say HSM migrated datasets with IMBED and REPLICATE will have them removed if and when they're recalled.
Workload Manager (WLM)
WLM got several enhancements. One addresses a frustrating problem when a cancelled job won't leave the system. With z/OS 1.9, WLM boosts the priority of these doomed jobs to get them out of the way. Likewise, IBM added "trickle" support, allowing shops to specify a smidgen of CPU for discretionary work even when the processors are near 100% busy.
Additional features
Here's a laundry list of other items. Apologies if these are important to your shop, but I gave them the short shrift:
A pretty good crop of enhancements with this new release.
ABOUT THE AUTHOR: Robert Crawford has been a CICS systems programmer off and on for 24 years. He is experienced in debugging and tuning applications and has written in COBOL, Assembler and C++ using VSAM, DLI and DB2.
