[Default] On 23 Jan 2018 17:35:50 -0800, in bit.listserv.ibm-main [email protected] (Ron hawkins) wrote:
>Clark, > >If you had time to read through this lengthy thread you will find that the >2nd file uses skip-sequential access. LSR is usually not an appropriate >strategy for this access pattern. I realize he was using skip sequential. My point was that random access looks like it could be a better fit for this file than skip sequential especially since a second record may have to be read after the first record is found on the second file. Clark Morris > >The OP has tried reducing BUFND on the second file, and observed a reduction >in throughput, which verifies the extent to which the sequential access is >taking advantage of chained Cis. > >Ron > >-----Original Message----- >From: IBM Mainframe Discussion List [mailto:[email protected]] On >Behalf Of Clark Morris >Sent: Tuesday, January 23, 2018 4:57 PM >To: [email protected] >Subject: Re: [IBM-MAIN] VSAM Performance - CPU reduction > >[Default] On 5 Jan 2018 16:28:48 -0800, in bit.listserv.ibm-main >[email protected] (Arun Venkatratnam) wrote: > >>Hi All, >> >>We are looking to improve the performance of a COBOL program that processes >2 VSAM files. The first file is the I/P file and every record read from the >input VSAM file is searched for a matching record in the other file and a >report is written. The program also applies some business rules while >comparing each matching record. >> >>The I/P file is read sequentially while the other file is read in a skip >sequential basis. The test files that were used had 32M records each while >production files have 110M records each. > >I assume using random access for the second file was tried with adequate >buffering for index and data. BLSR or the more current means of doing random >access buffering should have been used. It may also help to save any >randomly read record that were read based on information in records from the >second file based on the match with a record from the first file. Knowing >access patterns can help in determining the best solution. > >Clark Morris >> >>Attached is the strobe report from the execution of the test job. The test >job takes nearly 7 CPU minutes and was profiled to capture about 1 CPU >minute of execution time. >> >>We are attempting to optimize the VSAM access to these files as it is seen >to take more than 50% of the CPU consumed by this job. >> >>In the 'Attribution of CPU execution time' section, we see that the major >contributors are the components 'QSAM INIT I/O & EXITS' (Module IGZEQBL) >and PARTITION COMMUNICATION. >> >>Could you please help us understand: >> >>1.What these components are >>2.Why is QSAM access used instead of VSAM I/O access. >>3.What needs to be done to reduce the CPU consumption by these components. >> >>Thank you >> >>Arun >> >> >>----------------------------------------------------------------------- >>----------------------------------------------------------------------- >>-------------------- >> >>1Strobe* PERFORMANCE PROFILE PROGRAMA >01/02/2018 PAGE 42 >> > >>- #ACE ** ATTRIBUTION OF CPU EXECUTION >TIME ** >>-.COBLIB IGZCPCO IGZEVIO VSAM INPUT/OUTPUT > >> ---------------------------WAS INVOKED BY--------------------- >-----------------VIA----------------------- CPU TIME % >> XACTION MODULE SECTION DESCRIPTION MODULE >SECTION DESCRIPTION SOLO TOTAL >> > >> .LELIB CEEBINIT LE/370 BATCH INIT/TERM >.32 32 >> .LELIB CEEBINIT LE/370 BATCH INIT/TERM IGZEQBL >QSAM INIT I/O & EXITS 1.93 1.93 >> > >> XACTION MODULE SECTION LOCATION LINE SOURCE TEXT MODULE >SECTION DESCRIPTION >> > >> PROGRAMA PROGRAMA 003522 >1.30 1.30 >> >----- ----- >> >3.55 3.55 >>-.VSAM IDA019L1 VSAM RECORD MANAGEMENT > >> ---------------------------WAS INVOKED BY--------------------- >-----------------VIA----------------------- CPU TIME % >> XACTION MODULE SECTION DESCRIPTION MODULE >SECTION DESCRIPTION SOLO TOTAL >> > >> .LELIB CEEBINIT LE/370 BATCH INIT/TERM IGZEQBL >QSAM INIT I/O & EXITS 1.84 1.84 >> .LELIB CEEBINIT LE/370 BATCH INIT/TERM IGZEQBL >CURRMEM QSAM INIT I/O & EXITS 4.34 4.38 >> .LELIB CEEBINIT LE/370 BATCH INIT/TERM IGZEQBL >DVFILE QSAM INIT I/O & EXITS .03 .03 >> .LELIB CEEBINIT LE/370 BATCH INIT/TERM IGZEQBL >PREVMEM QSAM INIT I/O & EXITS 22.48 22.51 >> > >> XACTION MODULE SECTION LOCATION LINE SOURCE TEXT MODULE >SECTION DESCRIPTION >> > >> PROGRAMA PROGRAMA 003522 IGZCPCO >CURRMEM PARTITION COMMUNICATION 4.15 4.19 >> PROGRAMA PROGRAMA 003522 IGZCPCO >IGZEVIO VSAM INPUT/OUTPUT .57 .57 >> PROGRAMA PROGRAMA 003522 IGZCPCO >PREVMEM PARTITION COMMUNICATION 16.80 16.80 >> >----- ----- >> > >> 50.22 50.32 >> >>---------------------------------------------------------------------- >>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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
