Classification: Confidential NO. IEFBR14 will allocate the space. However the dataset will not be opened.
-----Original Message----- From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of CM Poncelet Sent: Thursday, May 12, 2022 10:52 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: [EXTERNAL] Re: Potential Resource Savings Techniques [CAUTION: This Email is from outside the Organization. Unless you trust the sender, Don’t click links or open attachments as it may be a Phishing email, which can steal your Information and compromise your Computer.] I could be wrong, but I had the vague impression that allocating datasets via IEFBR14 did not *physically* allocate them on DASD - but that they were physically allocated only when an 'OPEN for WRITE' was issued against them. BTW I cannot check this, as I have no access to a mainframe (8+ years.) On 12/05/2022 15:06, Pommier, Rex wrote: > David, > > My point was that if you allocate the dataset with a very small > primary and large secondary, if the dataset is never opened, you've > only wasted a cylinder of space instead of 500. I just played with > Richard's suggestion of using SPACE(CYL(0,500),RLSE) and it works just > fine, allocating no space unless the dataset actually gets opened and > data written to it. For some reason I had it stuck in my head that > strange things happened if you set a primary space of 0 but that > doesn't appear to be the case. So even in my old age I learned > something. :-) > > Rex > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On > Behalf Of <David> <Mingee> > Sent: Wednesday, May 11, 2022 4:30 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: [EXTERNAL] Re: Potential Resource Savings Techniques > > Great technique. What utility or JCL is being used, if the dataset is not > opened then RLSE does not happen. > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On > Behalf Of Pommier, Rex > Sent: Wednesday, May 11, 2022 5:20 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: [EXTERNAL] Re: Potential Resource Savings Techniques > > David, > > Here's another solution to that scenario. We have several datasets that > historically got allocated like you show here on a nightly basis. The jobs > would either populate the datasets or not even open them. I had the > developer change the JCL to allocate them with SPACE(CYL(1,500),RLSE). > Dataset doesn't get populated? No problem, 1 cylinder used. If it gets > populated, it typically fills up 1 or 2 extents. No more huge amounts of > wasted space. > > Rex > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On > Behalf Of <David> <Mingee> > Sent: Wednesday, May 11, 2022 4:13 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: [EXTERNAL] Re: Potential Resource Savings Techniques > > My 2nd apology. The main reason for using this IDCAMS method is to > reduce wasted disk space for empty files. Sometimes empty files are > Updated with data after they are created and sometimes they just > remain empty. One user created a few hundred of these each month with > SPACE=(CYL,(500,200),RLSE) . So IDCAMS creating them saved 1000's of CYLs of > DISK. > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On > Behalf Of Paul Gilmartin > Sent: Wednesday, May 11, 2022 4:21 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Potential Resource Savings Techniques > > On Wed, 11 May 2022 15:36:01 -0400, wrote: > >> I apologize to all. The Correct JCL is below. It must use INFILE of DD >> DUMMY. >> > How do IEFBR14, IEBGENER, and IDCAMS compare in behavior and performance? > I'd expect: > IEFBR14 fails to RLSE. > IEBGENER is simplest to code for a single data set. > IDCAMS has best performance for multiple data sets because it minimizes job > step overhead. > > Is there any purpose in allocating a primary with multiple storage units > then immediately RLSE, other than demonstration? > > I recall I was told that the EOF is written automatically if the SMS address > space is active, regardless whether the data set is SMS managed. > > How does this play with data recovery by allocating with ABSTRK? > > I prefer BLKSIZE=0. SDB knows best. > >> IDCAMS TO ALLOCATE EMPTY FILE VS USING IEFBR14 AS BR14 DOES NOT USE >> SDB or RLSE SPACE >> //STEP010 EXEC PGM=IDCAMS >> //DD1 DD DUMMY CAN USE DD DUMMY OR DD * WITH NO DATA >> //DD2 DD DSN=GRT.GIOIDXM.TEST.BLK1(+1), >> // DISP=(NEW,CATLG,DELETE), >> // DCB=(BLKSIZE=0,DSORG=PS,LRECL=80,RECFM=FB), >> // SPACE=(CYL,(100,200),RLSE),UNIT=DISK >> //DD3 DD DSN=GRT.GIOIDXM.TEST.BLK2, >> // DISP=(NEW,CATLG,DELETE), >> // DCB=(BLKSIZE=0,DSORG=PS,LRECL=80,RECFM=FB), >> // SPACE=(TRK,(180,180),RLSE),UNIT=DISK >> //SYSPRINT DD SYSOUT=* >> //SYSIN DD * >> REPRO INFILE(DD1) OUTFILE(DD2) >> REPRO INFILE(DD1) OUTFILE(DD3) >> /* > -- > gil > > ---------------------------------------------------------------------- > 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 > > ---------------------------------------------------------------------- > The information contained in this message is confidential, protected from > disclosure and may be legally privileged. 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