Bruce, Here are the places where SMS writing an EOF is documented. z/OS V1R7.0 DFSMS Using Data Sets
When the system allocates a new SMS data set with DSORG=PS or no DSORG, the access methods treat the data set as being null, that is, having no data. A program can safely read the data set before data has been written in it. This means the first GET or first CHECK for a READ causes the EODAD routine to be called. z/OS V1R7.0 DFSMS: Implementing System-Managed Storage For sequential data sets, SMS writes a hardware EOF at the beginning of the data set at initial allocation. This prevents data integrity problems when applications try to read the data before data is written in the data set. Doug On Wed, 24 May 2006 11:00:21 -0400, Bruce Black <[EMAIL PROTECTED]> wrote: >Art, I believe you are right, but I can never remember the exact rules >to get the EOF written. I searched the FMs once, but I don't think it >is documented. > >but actually DS1LSTAR is still zero in that case. the EOF is record 1, >so the last "data block" is "record 0". You can't tell the difference >from LSTAR. > >As for Gil's suggestion that the access method should not allow you to >read past LSTAR, in the past it was not uncommon for LSTAR to be >inaccurate. It is updated at CLOSE but if CLOSE fails or system crashes >or whatever, the DSCB may not get updated. There may be lots of valid >data past the LSTAR. Not so common today but can happen. > >-- >Bruce Black >Senior Software Developer >Innovation Data Processing ---------------------------------------------------------------------- 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
