Kenneth J. Kripke wrote: > Hello; > I was curious what the 16 bytes in front of the JFCB is. I extract the 3 byte ADDRESS of the JFCB > from the TIOT, and, then need to step past a 16 byte area in front of the actual JFCB. What is contained in the 16 byte area? > I have tried to make some sense of it. > > Sincerely; > > Ken Kripke > [email protected] > You might like to do a Google search on "swareq", "swa queue", "iefjsswa", "iefqmraw" and "iefqmreq". You'll find lots of information, and including reference to "swareq", a macro that you can use to access SWA (Scheduler Work Area) depending on whether it is in low or high storage. SWAREQ and similar macros automatically take into account the 16 byte prefix, and convert the "token" into real addresses.
Bit of history: JCL is converted into 176 byte control blocks, and stored in the Scheduler Work Area. The Job Card, Exec Card and DD Cards are converted into the JCT, ACCT, SCT, TIOT and JFCBs, and the PDQ (Passed Data Set Queue). As the job progresses, these block are read, changed and re-written into the SWA. Now, the SWA was originally stored in a data set called SYS1.SYSJOBQE in MFT and MVT. With VS1, it was optionally in storage. SVS stored it in storage, I think. MVS certainly did. And with Z/OS, it was in storage, and later, it moved above the line. When the SWA was a data set, the addresses were TTR addresses, and you could read and write the Job Queue with BSAM, and a few Points, Reads etc. When it was moved into main memory, Tokens were used instead of TTRs. And when it moved above the line, these tokens can be converted into 4 byte addresses (remember, many TTR addresses were three bytes in the SWA, and a lot of the control blocks couldn't be readily changed to 4 bytes). When MVS was introduced, IEFQMRAW was used to access the JobQ, and it automatically converts addresses for us. When the SWA or JOBQ was moved to main memory, a prefix was inserted that contained information that could be used to chain the control blocks together, and similar. Hope that helps, Clement Clarke Author, Jol - the JCL and CLIST Replacement Language ---------------------------------------------------------------------- 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
