> In theory, using EXCP, you could read using CCWs with data chaining > that would read multiple blocks in one I/O operation and concatenate them > into one data area.
Only if you used Read Multiple CKD; given that SAM-E is bundled into z/OS, I'm not convinced that you'd get a noticeable performance boost. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List [[email protected]] on behalf of Walt Farrell [[email protected]] Sent: Tuesday, March 2, 2021 12:30 PM To: [email protected] Subject: Re: Large block interface for VB On Mon, 1 Mar 2021 09:12:59 -0500, Joseph Reichman <[email protected]> wrote: >I have 100 files concatenated that are normally processed by qsam with a lrecl >31996 and blksize 32000 > >Since processing takes a long time I was looking to speed things up by >specifying a blksize of 320000 in the DCBE > >After the first read using bsam read macro I looked at the first 4 bytes ( >Block descriptor word ) and it was x’7C4A’ which is 31,888 which seemed to me >that it was still processing blksize of 32,000 I'm surprised no one has mentioned it, but for input files, the blocksize is determined by the application that wrote the file. The application that is reading has no control over it. If you're reading a block, it is as long as it is, and no longer. In theory, using EXCP, you could read using CCWs with data chaining that would read multiple blocks in one I/O operation and concatenate them into one data area. But that would be complex, and (I think) unlikely to get significantly better performance than simply increasing the number of channel programs that QSAM uses. -- Walt ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
