On Aug 8, 2012, at 18:51, Shmuel Metz (Seymour J.) wrote: > >> Does this mean that if the current record spans several blocks, >> setting the z byte causes enough intervening blocks containing >> enough segments to be skipped that the block read contains the first >> segment of the next record? > > No; TTR1 will access the next physical record. BSAM doesn't deal with > the RDW. > In:
http://publibz.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/DGT2D4A0/3.8.7.8 (which I trimmed too much and, now that I read the outline hierarchy, refers to PDSEs), I read: 3.8.7 Processing a Member of a PDSE 3.8.7.8 Using the POINT Macro to Position to a Block The POINT macro positions to the first segment of a spanned record even if the NOTE was done on another segment. If the current record spans blocks, setting the z byte of the TTRz field to one lets you access the next record (not the next segment). So I conclude that if the current "block" (itself a slippery concept with PDSEs) contains only an interior segment of a spanned record, POINT to a TTRz will cause the following READ to read the block containing the first segment of that [logical] record, and POINT to a TTR1 will cause the following READ to read the block containing the first segment of the next [logical] record. It's still pretty amazing. THis could be a point of incompatibility between PDSE and PDS. Who keeps spanned records in a PDSE or PDS, anyway? -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN