what will happen if i free or release a partitioned data set



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what will happen if i free or release a partitioned data set

Postby whiz18 » Sun Apr 24, 2011 6:15 pm

hi! Im new to tso/ispf, cobol programming, I just want to ask what will happen if i free or release a partitioned data set tso/ispf using the FREE command? The PDS library is expected to grow. I accidentally hit the F button rather than than the V button. I hope to get a reply soon. thanks :)
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Re: what will happen if i free or release a partitioned data set

 

Re: what will happen if i free or release a partitioned data

Postby MrSpock » Sun Apr 24, 2011 6:47 pm

In ISPF, the FREE option (line command F) will release the unused space for the specified dataset. If it grows, you may have to add more space sometime in the future. Personally, I'd run this by the storage team and see if there might be any impact in the future. The TSO FREE command de-allocates the dataset allocation from your TSO session.
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Re: what will happen if i free or release a partitioned data

Postby steve-myers » Thu Apr 28, 2011 7:54 pm

There is one important consideration to MrSpock's analysis. Only unused space following the last physical member in the dataset is released. Unused space created by deleting members is not released.
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Re: what will happen if i free or release a partitioned data

Postby whiz18 » Thu Apr 28, 2011 8:52 pm

thanks for the replies.

I read somewhere that it's different when the SPACE allocated for the dataset are CYLINDERS?

"Only unused space following the last physical member in the dataset is released"

so that mean I cant add another member to the dataset if it was released?
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Re: what will happen if i free or release a partitioned data

Postby NicC » Thu Apr 28, 2011 10:54 pm

so that mean I cant add another member to the dataset if it was released


1 - what happened when you tried?
2 - no. another extent will get allocated
The problem I have is that people can explain things quickly but I can only comprehend slowly.
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Re: what will happen if i free or release a partitioned data

Postby steve-myers » Fri Apr 29, 2011 7:21 am

whiz18 wrote:thanks for the replies.

I read somewhere that it's different when the SPACE allocated for the dataset are CYLINDERS?

"Only unused space following the last physical member in the dataset is released"

so that mean I cant add another member to the dataset if it was released?

It depends.
  • The size of the new member.
  • The actual allocation and space available after the space release function completes. I had originally thought to write a much more comprehensive reply, but I canceled that idea after a couple of experiments. There were too many variables to simplify it for a beginner. As NicC says, the system usually can allocate a new extent.
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Re: what will happen if i free or release a partitioned data

Postby steve-myers » Fri Apr 29, 2011 11:12 am

I ran this job --
//JOBLIB   DD  DISP=(SHR,PASS),DSN=&SYSUID..LOAD
//         DD  DISP=(SHR,PASS),DSN=&SYSUID..OLOAD
//A       EXEC PGM=IEFBR14
//PDSGAS   DD  DISP=(MOD,DELETE),UNIT=SYSALLDA,SPACE=(TRK,0),
//             DSN=&SYSUID..TESTPDS.PDSGAS
//SYSTSPRT DD  DISP=(MOD,DELETE),UNIT=SYSALLDA,SPACE=(TRK,0),
//             DSN=&SYSUID..TESTPDS.SYSTSPRT
//B       EXEC PGM=PDSGAS
//SYSPRINT DD  DISP=(,PASS),UNIT=SYSDA,SPACE=(TRK,(1,1))
//SYSUT1   DD  DISP=SHR,DSN=&SYSUID..ASM
//C       EXEC PGM=IKJEFT01
//SYSTSPRT DD  DISP=(,PASS),UNIT=SYSDA,SPACE=(TRK,(1,1))
//SYSTSIN  DD  *
LISTD ASM LABEL
//D       EXEC PGM=CNVTM
//SYSPRINT DD  SYSOUT=*
//SYSUT1   DD  DISP=(OLD,DELETE),DSN=*.B.SYSPRINT
//SYSUT2   DD  DISP=(,CATLG),UNIT=SYSDA,SPACE=(TRK,(1,1)),
//             DSN=*.A.PDSGAS
//E       EXEC PGM=CNVTM
//SYSPRINT DD  SYSOUT=*
//SYSUT1   DD  DISP=(OLD,DELETE),DSN=*.C.SYSTSPRT
//SYSUT2   DD  DISP=(,CATLG),UNIT=SYSDA,SPACE=(TRK,(1,1)),
//             DSN=*.A.SYSTSPRT

PDSGAS is a program that analyzes a PDS to "undelete" members, though this run just produces the report. CNVTM is a program to preoare a dataset using carriage control for a PC based word processor, though I usually display the data using Windoze NOTEPAD.

Part of the output from PDSGAS is --
FLAT2PDS 001801 001801 001902 079E000901 079E000A02
*****GAS        001903 001A02 079E000A03 079E000B02
PDS2FLAT 001A03 001A03 001B02 079E000B03 079E000C02
*****GAS        001C01 001C03 079E000D01 079E000D03
RETCODE  001C04 001C04 001C05 079E000D04 079E000D05
*****GAS        001D01 001D03 079E000E01 079E000E03
INVOKE   001E01 001E01 001E03 0634000001 0634000003
"Member" entries marked as GAS represent the space occupied by deleted members. The last member is INVOKE, it starts at TTR 001E01 and ends at TTR 001E03. 0634000001 0634000003 are the disk addresses of the first and last records.

The output from the TSO step is -
LISTD ASM LABEL
XXXXXX.ASM
--RECFM-LRECL-BLKSIZE-DSORG
  FB    80    27920   PO
--VOLUMES--
  XXXXXX
--FORMAT 1 DSCB--
F1 C6E4E2D9F1C5 0001 6E00E5 000000 02 00 00 C9C2D4D6E2E5E2F24040404040
6F0076A0000000 0200 90 00 6D10 0050 00 0000 82 C0000001 001E03 4532 0000
8100079D0000079E000E 8101063400000634000E 00000000000000000000 0000000000

The LABEL option tells the LISTDS command to display the contents of the DSCBs for the dataset, in hexadecimal. The C0000001 are codes to indicate the secondary allocation is 1 cylinder. 001E03 4532 The first 6 digits show the TTR of the last record in the dataset. The 4532 is the remaining space on the track, this translates to 17714, but not all of that space can actually be used for data. 8100079D0000079E000E 8101063400000634000E are the extent entries for the dataset. A skilled analyst can quickly deduce the first extent has 2 cylinders, and the second extent has 1 cylinder.

Now, what would happen if I tried the ISPF FREE function for this dataset? Actually, nothing, since part of the second extent contains data.

If I add another member, the system will attempt to use the remainder of the last used track, and then continue using the remaining tracks in the extent.
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