In article <[EMAIL PROTECTED]>, Tom Marchant <[EMAIL PROTECTED]> wrote:
> I don't follow you here Bill. Of course the control unit doesn't know about > any > logical data structures. It does, however, have to keep track of where all > data is located. If there is a copy of a track in cache, it has to know > about > that and always ensure that the correct copy is updated or returned. The > fact that there has been a request to destage the track from cache does not > alter that. Step A writes a lot of data, and then issues CLOSE, leading to a Channel Command of "Asynchronous Commit" being sent to the storage controller for all the tracks of all of Step A's data sets. That Commit may take a long time to complete, but as far as Step Management is concerned, the data sets are already closed and available for allocation. Step B allocates the same dataset, and thus some of the not-yet-committed tracks, but will appear to hang when it attempts to write, as the storage controller cannot allow writes to those tracks to happen until the commit of Step A's data is complete. Step B's unexpected delay may even lead to the job's failure, perhaps with a S522 or S222 abend. -- Randy Hudson ---------------------------------------------------------------------- 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
