Hi, Like others have suggested BLSR or SMB ACCBIAS=DO is the way to go if the VSAM is accessed in a non-sequential manner (which seems to be the case, giving the IAM vs. VSAM performance difference you've encountered).
Also, from the "LISTCAT", if I read it correctly, many records seem to be updated so a DEFER WRITE (DFR) should be considered (and may or may not be enabled by default). Take a look at http://publib.boulder.ibm.com/infocenter/zos/v1r12/index.jsp?topic=%2Fcom.ib m.zos.r12.idad400%2Fsmbt.htm. Best Regards, Yifat -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Brown, Larry - RD, St. Louis, MO Sent: Thursday, July 19, 2012 3:22 PM To: IBM-MAIN@LISTSERV.UA.EDU 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. Any unauthorized interception of this message or the use or disclosure of the information it contains may violate the law and subject the violator to civil or criminal penalties. If you believe you have received this message in error, please notify the sender and delete the email immediately. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
