Funny you should ask. I'm working on a CMG paper about Java on z/OS right now. The overhead is not nearly as bad as it used to be, and on modern hardware, especially with zAAPs (or zAAP on zIIP to forestall that point), probably immaterial for a lot of things. But you specifically said that zAAPs weren't in the mix, which is unfortunate.
I've also done a fair bit of REXX SDSF. It works pretty well, most of the time. And personally, I like REXX more than Java. If you're talking about using the JZOS MvsJobOutput class, the doc for that states: "The class relies on the sample Rexx script "jobOutput", spawned as a child process via the Exec class." I haven't looked at that script, but my guess is that it's using the REXX SDSF interface. So in this case the Java solution = Java overhead + REXX SDSF. That sum will be greater than either part, so I'd just stick with REXX unless I was doing substantial further processing of the output that could be zAAP- eligible. Of course if I was a Java only programmer, and didn't know REXX programmer, then I'd probably have to use the Java class. As for the overhead of instantiating the JVM, that's down to < 1 CPU second for trivial work, even on a z10-504 (half speed CPs). But it's still tenths of a second, so you probably don't want to be instantiating multiple per second unless you have the CPU to back it. (Almost all of that is zAAP-eligible though.) If you're talking about a few requests per hour though, you probably don't care. For truly trivial (not much beyond "helloWorld"), look at the "quickstart" runtime option. That does seem to have a noticable impact on those trivial results. It does seem to potentially have a negative impact on longer running things though. I think caching shared classes may also help in cases where you're starting the same Java class multiple times per day, but I haven't yet investigated this. And if you're in the Cincinnati area, I'm presenting on this topic at the Cincinnati System Z User Group on 6/23. I expect to have a better summarization of performance data re. running Java in batch on z/OS. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
