If you issue a BSAM READ followed by a WAIT, and then deblock the buffer before doing the next READ, the system builds a channel program to read just the one block. If on the other hand you issue 10 READ commands in a loop, each READ having its own DECB, the system will build a channel program to read the first block and then because the other 9 commands are presented before the first has finished, it will build a chained channel program to read the 9 in one physical I/O operation. Now there is a fair amount of overhead for each I/O, and the time for each block is much less than that, so you wind up reading a lot faster. You can build a very efficient BSAM process, but it is not for the faint of heart. As I said, QSAM with a reasonably large BUFNO, like 20 or more, will get you 90 to 95% of the way.
Chris Blaicher Technical Architect Mainframe Development Syncsort Incorporated 2 Blue Hill Plaza #1563, Pearl River, NY 10965 P: 201-930-8234 | M: 512-627-3803 E: [email protected] www.syncsort.com CONNECTING BIG IRON TO BIG DATA -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Joseph Reichman Sent: Friday, February 3, 2017 2:27 PM To: [email protected] Subject: Re: BSAM vs QSAM I have huge VB files Don't really understand what you mean by Deblock after doing a READ then WAIT Where an entire block is read subsequent READs Just point to the next record > On Feb 3, 2017, at 2:22 PM, Blaicher, Christopher Y. <[email protected]> > wrote: > > There can be if you code for just what you expect. > > QSAM does multi-buffer I/O for you, with BSAM you have to issue multiple > WRITE or REAAD commands and do a WAIT, not to mention having to block or > de-block the buffer, which can be a real pain for VBS files. > > It really depends on how much you are processing and how often you are doing > it to determine if the amount of time you are going to spend on developing it > makes it worth it. > > Using QSAM with GET LOCATE (as long as you aren't processing VBS files) and a > reasonable BUFNO of 10 or more is going to get you close to most BSAM > applications. GET or PUT with the MOVE option is the easiest to code for. > > Chris Blaicher > Technical Architect > Mainframe Development > Syncsort Incorporated > 2 Blue Hill Plaza #1563, Pearl River, NY 10965 > > P: 201-930-8234 | M: 512-627-3803 > E: [email protected] > > www.syncsort.com > > CONNECTING BIG IRON TO BIG DATA > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] > On Behalf Of Joseph Reichman > Sent: Friday, February 3, 2017 1:51 PM > To: [email protected] > Subject: BSAM vs QSAM > > Hi > > BSAM is a bit more complex than QSAM > > Is there any performance improvement > > Thanks > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send > email to [email protected] with the message: INFO IBM-MAIN > > ________________________________ > > > > ATTENTION: ----- > > The information contained in this message (including any files transmitted > with this message) may contain proprietary, trade secret or other > confidential and/or legally privileged information. Any pricing information > contained in this message or in any files transmitted with this message is > always confidential and cannot be shared with any third parties without prior > written approval from Syncsort. This message is intended to be read only by > the individual or entity to whom it is addressed or by their designee. If the > reader of this message is not the intended recipient, you are on notice that > any use, disclosure, copying or distribution of this message, in any form, is > strictly prohibited. If you have received this message in error, please > immediately notify the sender and/or Syncsort and destroy all copies of this > message in your possession, custody or control. > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
