Knutson, Sam wrote:
My chief complaint with the current iteration of IOF is that it uses APPC for cross system communication almost as arcane as SDSF using MQSeries. I have not used E(JES) but understand it uses XCF a sensible and simple choice in a Sysplex and one that is familiar to the MVS or JES systems programmer likely to be doing the installation of the SPOOL browser.
XCF is even more beneficial than people might think, especially in larger configurations.
Many are aware of the performance benefits associated with running in SRB mode as all XCF exits do. [SRB mode exit processing is also possible for authorized VTAM/APPC applications when SRBEXIT=YES is coded on the VTAM APPL statement. MQ is TCB mode only.] But most are probably unaware that XCF also supports high-performance, unordered message delivery in which the SRBs running the message delivery exits are scheduled into the target address space in an unsynchronized manner.
For example, if ten messages arrive at nearly the same time, the SRBs to receive/process all ten of them will be scheduled into the target address space nearly simultaneously and, assuming ten or more CPs are available in the configuration, all ten SRBs could be running in parallel, delivering their respective messages to the XCF application, at precisely the same time!
Effectively leveraging unordered XCF message delivery requires more programming effort because the application must be designed to handle the bulk of the messages without queuing them for later sequential processing (an action that would "undo" most of the performance benefits associated with unordered delivery). Such programming is more complex, but need not add any appreciable run time overhead -- at least it doesn't in my code. :-)
It's like comparing USPS, UPS, and FedEx. The package gets there in all three cases. But FedEx gets it there faster. Unfortunately, that analogy falls apart as soon as you look at the costs involved because the message delivery performance does not increase with the price of the message delivery infrastructure. Only MQ is a cost option. The other two are included "free" with the operating system.
Of course, XCF is limited to sending messages within a sysplex. VTAM/APPC and MQ can send messages anywhere, even outside z/OS.
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