McKown, John wrote:
This is likely a crazy question. But I'm wondering if anybody has come up with a way to do what I will call an asynchronous open of a tape or disk file? Basically, what I want to do is an OPEN with an ECB= operand. When the OPEN completes, the ECB is posted with the return code from OPEN. Why? So that I can do other things while, perhaps, a tape is being mounted. Things such as doing other BSAM type async I/O, or TCP/IP communications, or operator communications via a MODIFY, all with a STIMER REAL going which invokes an async exit which POSTs as "time out" type ECB.
It's fairly simple to do, providing you're willing to abandon system access methods. In authorized code (program, PC routine, or SVC) you can issue I/O at will, although it's preferable if you allocate the device first (if it's other than DASD), and are aware of potential error and recovery situations. To get system support for routine error recovery, DDR, and output on dumps, it helps to build a DEB, DCB, and IOB, make sure the pointers are consistent, etc. All I/O can be carried out by system routines (STARTIO, EXCPVR, EXCP, XDAP) and is fairly simple once you get it working. Requests are made with ECBs, so you can choose whether or not to wait, use a subtask, etc. A simple ECB option on OPEN might be insufficient, as you'd presumably also want the option on EOV and CLOSE?
Gerhard Postpischil Bradford, VT ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
