Described in detail in the DFSMS Using Datasets manual, see https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.1.0/com.ibm.zos.v2r1.idad400/uoiowb.htm Includes sample code
On Tue, Mar 2, 2021 at 1:38 PM Joseph Reichman <[email protected]> wrote: > For NCP do you have to have a counter of the number of reads you do till > you do a check > > > > On Mar 1, 2021, at 7:34 PM, Joseph Reichman <[email protected]> > wrote: > > > > Thanks I’ll look Into it > > > >> On Mar 1, 2021, at 7:16 PM, Farley, Peter x23353 < > [email protected]> wrote: > >> > >> Joseph, > >> > >> Apologies, I mis-remembered what SMB can do. SMB is available only for > VSAM files, not for concatenated QSAM files. BLSR is one of two options > for many-buffered QSAM input. > >> > >> The other option is to use the regular DD parameters NCP=nn,BUFNO=nn > (max of 99 for each one) that may or may not help with I/.O performance. I > have run some work with NCP=99,BUFNO=99 with some helpful effects, though > not dramatic. > >> > >> To really take advantage of NCP/BUFNO you probably would need to code > to juggle "NCP" different READ's at a time using BSAM and your own > de-blocking subroutine. Lots of bookkeeping to keep track of them all and > only CHECK in the correct order. Robust recovery from I/O errors in such > code is also a thorny problem. Solvable, but thorny. > >> > >> Peter > >> > >> -----Original Message----- > >> From: IBM Mainframe Discussion List <[email protected]> On > Behalf Of Farley, Peter x23353 > >> Sent: Monday, March 1, 2021 1:43 PM > >> To: [email protected] > >> Subject: Re: Large block interface for VB > >> > >> EXTERNAL EMAIL > >> > >> You assume correctly, it does. In my experience both BLSR and SMB will > handle concatenations of any size without any issue. > >> > >> When using BLSR your primary DD (the one your program reads) is coded > with he BLSR parameters and nothing else, that DD then points (via a BLSR > parameter) to a second DD where you put your large concatenation. > >> > >> SMB is applied directly to your primary DD name, specify the SMB > parameters on only the first of the concatenated DD's. > >> > >> Peter > >> > >> -----Original Message----- > >> From: IBM Mainframe Discussion List <[email protected]> On > Behalf Of Joseph Reichman > >> Sent: Monday, March 1, 2021 1:36 PM > >> To: [email protected] > >> Subject: Re: Large block interface for VB > >> > >> Thank you I’m doing searches for files so I have over 100 concatenated > files does the access matters I mean I assume QSAM reads a block under the > covers > >> > >> > >> > >>>> On Mar 1, 2021, at 1:26 PM, Farley, Peter x23353 < > [email protected]> wrote: > >>> > >>> Joseph, > >>> > >>> I believe that LBI is only for tape inputs and outputs. You can speed > up your processing easier by using either the older BLSR buffering > subsystem or better the newer SMB buffering system. See the JCL reference > manual for SMB parameters. > >>> > >>> Allocate as much REGION as your installation will allow (some > installations limit the maximum any job without special authorization may > use, even sometimes production jobs). > >>> > >>> Use BLSR or SMB to allocate as many buffers as will fit in the REGION > size you can allocate. > >>> > >>> I have seen substantial decreases in run time using these techniques > with very large sequential files. > >>> > >>> I would also recommend using at least software compression or better > hardware compression (if your CPU has it) for your large sequential files. > The CPU time used for compression and decompression will sometimes be > offset by decreases in elapsed time due to reduced I/O burdens for the > compressed data, especially if you have hardware compression available. > >>> > >>> HTH > >>> > >>> Peter > >>> > >>> -----Original Message----- > >>> From: IBM Mainframe Discussion List <[email protected]> On > >>> Behalf Of Joseph Reichman > >>> Sent: Monday, March 1, 2021 1:14 PM > >>> To: [email protected] > >>> Subject: Re: Large block interface for VB > >>> > >>> Who uses tape > >>> > >>> I went to bsam trying to speed up my application wonder if going to > >>> bsam > >>> > >>> Does anything positive for me > >>> > >>>>>> On Mar 1, 2021, at 1:10 PM, Paul Gilmartin < > [email protected]> wrote: > >>>>>> > >>>>>> On Mon, 1 Mar 2021 11:24:57 -0500, Joseph Reichman wrote: > >>>>>> > >>>>>> It disk then documentation says the system only supports tape at > this time is That true ? > >>>>>> > >>>> Have you any reason to doubt it? > >>>> > >>>> I suspect it's a hardware limitation. > >>>> > >>>>>>> On Mar 1, 2021, at 11:22 AM, Paul Gilmartin wrote: > >>>>>> > >>>>>> On Mon, 1 Mar 2021 09:12:59 -0500, Joseph Reichman 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 > >>>>>>> > >>>>>> What device type? > >>>>>> > >>>>>>> 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 > >>>> > >>>> -- gil > >>>> > >> -- > >> > >> This message and any attachments are intended only for the use of the > addressee and may contain information that is privileged and confidential. > If the reader of the message is not the intended recipient or an authorized > representative of the intended recipient, you are hereby notified that any > dissemination of this communication is strictly prohibited. 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