I supported the IAM product at my prior employer for almost 20 years. When we acquired the IAM product I remember two jobs we had that read a moderately sized file that took 4 hours to run as VSAM. After enabling IAM these jobs ran in only 10 minutes. Since IAM maintains the 'entire' index, both upper and sequence set, in memory frequently half or more I/O's are eliminated. It's difficult to say without knowing the application but I would say your 14 hour execution time for VSAM is valid in your case and you may not be able to achieve close to the original execution time through buffer overrides if the application is 'bouncing' all over a sizeable file. You may contact be off list if you desire additional information.
Robert Rankin MVS System Programmer(Retired) [email protected] On Thu, Jul 19, 2012 at 11:58 AM, McKown, John < [email protected]> wrote: > "cold adult beverage". Hum, 18 year old iced tea? Or perhaps you meant > Macallan 18. Very generous of you: $139.99 for 750 ml at Amazon. Of course, > 18 is in the U.S. More adult would be 21, but that's $235.99 for 750 ml. > > -- > John McKown > Systems Engineer IV > IT > > Administrative Services Group > > HealthMarkets® > > 9151 Boulevard 26 . N. Richland Hills . TX 76010 > (817) 255-3225 phone . > [email protected] . www.HealthMarkets.com > > Confidentiality Notice: This e-mail message may contain confidential or > proprietary information. If you are not the intended recipient, please > contact the sender by reply e-mail and destroy all copies of the original > message. HealthMarkets® is the brand name for products underwritten and > issued by the insurance subsidiaries of HealthMarkets, Inc. -The Chesapeake > Life Insurance Company®, Mid-West National Life Insurance Company of > TennesseeSM and The MEGA Life and Health Insurance Company.SM > > > -----Original Message----- > > From: IBM Mainframe Discussion List > > [mailto:[email protected]] On Behalf Of Brown, Larry - > > RD, St. Louis, MO > > Sent: Thursday, July 19, 2012 1:49 PM > > To: [email protected] > > Subject: Re: Problem Going to VSAM from IAM > > > > Wow, the programmer dropped the bufsp parm, and his run time > > actually was better than before with IAM - under an hour. > > Again, many thanks to all who replied. If any of you are > > ever in St. Louis, let me know, and I'll buy you a cold adult > > beverage. > > > > Larry Brown > > Rural Development > > U.S. Department of Agriculture > > 4300 Goodfellow Blvd. > > St. Louis, MO 63120 > > Phone: 314.457.4939 > > > > -----Original Message----- > > From: IBM Mainframe Discussion List > > [mailto:[email protected]] On Behalf Of O'Brien, David > > W. (NIH/CIT) [C] > > Sent: Thursday, July 19, 2012 7:42 AM > > To: [email protected] > > Subject: Re: Problem Going to VSAM from IAM > > > > Larry, > > > > Your dd statement specifies space for 100 data buffers (4096 > > x 100 =409600) but you then specify bufnd=181, which is one > > cyl for a 4096 CI size, plus Bufni=9. I would lose the bufsp > > parameter and let VSAM allocate buffers according to the > > Bufnd and Bufni parameters. > > > > You might also code Rmode31=buff to allocate the buffers > > above the line. You didn't mention whether you were paging > > during the job execution. > > > > Regards, > > Dave O'Brien > > > > -----Original Message----- > > From: Brown, Larry - RD, St. Louis, MO > > [mailto:[email protected]] > > Sent: Thursday, July 19, 2012 8:22 AM > > To: [email protected] > > Subject: Problem Going to VSAM from IAM > > > > Hello, we have a job that was previously using Innovation's > > IAM file access method. The file is over 6 million records. > > The job runs twice yearly and usually takes an hour or less > > to complete. The product was removed to save on SW costs, > > and the file was converted to VSAM. The programmer did not > > make any other changes, and the job now takes over 10 hours > > to complete. I know the IAM product is supposed to improve > > performance, but can't imagine it making the difference > > between 1 and 14 hours run time. I'm suspecting there may > > have been some JCL changes to blksize, buffers, and things > > like that required, but the programmer is unaware of any of > > those changes he should have made. The job is only reading > > the file. Does anybody have any ideas on where to start > > looking for other changes that should have been made after > > converting from IAM to VSAM? The programmer is reviewing his > > source code. Our performance support has not suggested > > anything. Innovation claims %50-%80 reduction in processing > > time, so maybe it is just a matter of IAM vs VSAM.(?) > > > > Here are the JCL and VSAM definitions: > > > > //MISC DD DSN=ASLP00.FT.MISC,DISP=SHR, > > // AMP='BUFSP=409600,BUFND=181,BUFNI=9' > > > > Cluster: 'ASLP00.FT.MISC' > > + multi-volume > > Data: 'ASLP00.FT.MISC.DATA' > > Data Volume: PEST06 + > > Index: 'ASLP00.FT.MISC.INDEX' > > Index Volume: PEST06 + > > Data Component Information: Current > > Allocation Options: > > Device type: 3390 > > Load option: SPEED > > Organization: KSDS EXT-ADDR > > Write check: NO > > KSDS key length: 27 > > Buffer space: 10752 > > KSDS key location: 1 > > Erase on delete: NO > > Average record size: 80 > > Imbedded index: NO > > Maximum record size: 4084 > > Replicated index: NO > > Allocated Space: Unit Primary Secondary > > Reuse option: YES > > Data: CYLINDERS 2000 2000 > > Share option: 2-3 > > Index: CYLINDERS 300 30 > > Spanned records: NO > > Dataset Date Information: Key > > ranges present: NO > > CLUSTER - ASLP00.FT.MISC > > Storage: PESTBU > > > > Data: X4GB > > > > Management: MGTPSF > > > > Owner ID: > > - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - > > - - - - - - - - - > > Current Allocations in Tracks: Current Utilization > > in Tracks: > > Allocated space: 240000 Used data > > space: 198827 ( 83 %) > > Allocated extents: 2 Used > > extents: 2 ( 100 %) > > Allocation type: UNIQUE Prime > > records: 6,770,095 > > KSDS Index Allocation in Tracks: Deleted > > records: 3134 > > Allocated space: 4500 Inserted > > records: 8700 > > Number of records: 14795 Updated > > records: 706460 > > - - - - - - - - - - - Current Reorganization Information - - > > - - - - - - - - - > > Data - Control Area Information: Control Interval > > Information: > > Physical record size: 4096 > > Size-data: 4096 Index: 2560 > > > > Thanks, > > > > Larry Brown > > > > > > > > > > > > > > > > > > This electronic message contains information generated by the > > USDA solely for the intended recipients. 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