Using the JNI interface, you can create the JVM once and then make as many method invocations as you like with it. There isn't a requirement to call CEEPIPI if you are doing this from C, since your LE Enclave will already be there.
Kirk Wolf Dovetailed Technologies https://coztoolkit.com On Thu, Jul 13, 2023, at 8:06 AM, Crawford Robert C (Contractor) wrote: > Denis, > > Thank you for the detailed answer. I'll start looking into your suggestions. > > I may be misunderstanding your question, but we would like a persistent JVM > so the assembler code can call Java classes as subroutines. Creating and > terminating a JVM for each call would be prohibitively expensive. > > Robert Crawford > Abstract Evolutions LLC > (210) 913-3822 > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of > Denis > Sent: Wednesday, July 12, 2023 8:30 AM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: [EXT] Re: Invoke Java from Assembler > > Hi Robert, > > IMS uses the CEEPIPI approach to make the JVM persistent, but thats actually > only needed if multiple modules are serially executed and (speaking with > COBOL) end with a GOBACK. The GOBACK of the first module called would > terminate the LE enclave (and as such the JVM) so CEEPIPI is used to allow > the next program to work the same way without tiering down the JVM. > The COBOL (and C JNI) work like this, you start a program e.g. with JCL > PGM=PROG1. Enterprise COBOL initializes the JVM (CreateJavaVM and > AttachCurrentThread JNI calls under the covers if I remember correctly, in C > and e.g. PL/I you do that by yourself and the environment for the JVM is > pointed to by _CEE_ENVFILE) and with that JVM pointer you can do any number > of JNI calls (e.g. call Java methods) and after each call the calling program > is returned control. The JNIEnvPtr will be valid as long as the JVM or the LE > enclave stay up.You can do the same thing in assembler, but you need an LE > enclave with POSIX(ON) and XPLINK(ON) since the JVM on z/OS is written in C > and requires those settings (in addition that up to Java 8 the 31bit version > of Java needs to be used). But if the inital assembler uses CEEENTRY and > CEETERM it will be quite easy to achieve, because it would create the LE > enclave and remain until the initial assembler ends. From that first module > you can call any non LE assembler as you like.The JVM can be ended by using > JNI call DestroyJavaVM to make sure any unfinished work on the Java side is > ended (as opposed to just end the first module and terminate the JVM together > with the LE enclave and the address space). > One question is, why would you need to make the JVM persistent with CEEPIPI > in batch?You can do PROG1 call anything then return, PROG1 call Java then > return as long and as many times as you want without the need of CEEPIPI and > reusing the JVM - since its not terminated after return from Java. > But to make it more complicated, since Java 11 for z/OS there is no 31bit JVM > anymore and the JVM will be in a secondary 64bit LE enclave. There is a > libjvm31.so shared library which can be used to make the JNI calls work, with > the difference that most references require 64bit parameters. (Under the > covers CEL4RO64 service is > used)https://www.ibm.com/support/pages/enhancement-coboljni-interface > > For now, I think the easiest way to do it, is in COBOL. > Hope that helps,Denis. > On Wednesday, July 12, 2023 at 02:40:08 PM GMT+2, Crawford Robert C > (Contractor) <000004e08f385650-dmarc-requ...@listserv.ua.edu> wrote: > > > Thanks, Allan. > > Back in the 90's I used CEEPIPI to create a persistent C enclave I could call > from Assembler because building the environment is expensive. Unfortunately, > CEEPIPI documentation is kind of scarce. What we do find doesn't give us > very many clues for how to get to Java. > > Robert Crawford > Abstract Evolutions LLC > (210) 913-3822 > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of > allan winston > Sent: Tuesday, July 11, 2023 5:22 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: [EXT] Re: Invoke Java from Assembler > > Robert, > > This reminds me of a situation I ran into 25 years ago involving assembler > and COBOL. Granted, COBOL and Java are different environments, but there may > be enough similarity in the issues to be relevant. > > We had an assembler main program that called a COBOL subroutine > repeatedly. It was chugging along just fine until LE maintenance showed a > large spike in CPU time within LE library routines, as shown by Strobe. > It seemed as though the LE environment was constantly being created and torn > down. I did look into solutions, such as using CEEPIPI, but this program was > a major CPU consumer in this shop and we needed a quick solution. The > solution I proposed and was implemented was to create a new main program, > written in COBOL, that called the former assembler main program. That way > the new main program established the LE environment that persisted until the > program terminated. > > So, ALC calling COBOL changed to COBOL calling ALC calling COBOL. > In your case: Java calling COBOL changed to COBOL calling Java calling COBOL. > > I have never used Java, so this is somewhat a shot in the dark. > > I should have created an ETR on IBMLINK about the increased CPU overhead, > but did not bother since we had a circumvention. > > Allan > > On Tue, Jul 11, 2023 at 5:58 PM Crawford Robert C (Contractor) < > 000004e08f385650-dmarc-requ...@listserv.ua.edu> wrote: > > > We're interested in invoking Java from assembler in batch. > > Specifically, we'd like to create a persistent Java environment we can > > call repeatedly and terminate when we're through. > > > > Has anyone done this? Is the LE pre-initialization module CEEPIPI > > worth exploring? > > > > Thanks. > > > > Robert Crawford > > Abstract Evolutions LLC > > (210) 913-3822 > > > > > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, send > > email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email to > lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email to > lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email to > lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
