| miggeman@gmail.com 2007-03-12, 7:55 am |
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This is my first post and I hope you can bear with me since english is
not my
native language. Thank you in advance!
Cheers,
Miguel
Background info:
z/OS version 01.07.01
IBM Enterprise COBOL for z/OS version 3.4.0
Enterprise COBOL for z/OS, Version 3 Release 4 Publications
http://www-306.ibm.com/software/awd...ol/zos/library/
Language Reference Manual
http://publibfp.boulder.ibm.com/epubs/pdf/igy3lr31.pdf
This is regarding file allocation from a COBOL program using a an
environmental
variable in the SELECT ... ASSIGN TO clause. That is, input and/or
output
from a COBOL program to a data set whose name has been dynamically
obtained.
I do not have any problem at all making the actual dynamic connection
between
my COBOL program and the reference to a physical file for reading or
writing.
I have so far with success managed to dynamically allocate files for
splitting
a large file into many several smaller files, all having the same
characteristics,
without any problems at all. Works like a charm.
I've used a normal COBOL program and called setenv for setting an
environmental
variable to contain a "DSN(...)" with all file attributes stated.
My problem lies in the allocation and the non-release of space
afterwards when the
file is closed in the program.
Normally when a file is created and written to from a cobol program,
the file
characteristics and attributes are defined in the COBOL program and in
the
JCL / procedure used to run the program.
Typically this is how a normal case would be solved without using an
environmental
variable in the SELECT ASSIGN -clause. The name in the ASSIGN is
stated with
the DD-statement:
//DYNAM DD DSN=P210.DEL1.TEST,
// DISP=(NEW,CATLG,KEEP),
// DCB=(RECFM=FB,LRECL=32),
// SPACE=(CYL,(50,10),RLSE)
The definition above would see to that the file P210.DEL1.TEST is
created with
the possibility to accomodate one record or up to the limit of
SPACE=(CYL,(50,10,RLSE).
The RLSE parameter attached to the SPACE keyword makes sure that all
superflous,
unused space is "returned" to the system when the file is closed or
the program ended.
The quantity CYL, 50 and 10 extents was picked to show my problem but
one would think
that it should not be a problem in the scenario of not knowing in
advance if the resulting
output file will accomodate 10 records or hundreds of thousands of
them. A mechanism
corresponding to the JCL and space-keyword and the attribute "RLSE
would take care of that,
if I'm correct.
The corresponding solution using a COBOL program but instead
explicitly *not* defining
a corresponding DD-card to the SELECT ... ASSIGN defintion in the
program works fine, but
with the quirk that the created file's remaining / superflous space is
never released.
In my test COBOL program the environvent-variable DYNAM is set by
calling the PUTENV program
with the null-terminated string DYNAM=DSN(P210.DEL1.TEST) NEW CYL
SPACE(50,10) KEEP.
Nowhere have I found any mentioning of RLSE as a valid parameter to
use in the dynamic
allocation / use of QSAM files.
In the Language Reference Manual, I've read and re-read the sections
"4.2.3.1 Assignment name for environment variable"
where it says "[...]The contents of the environment variable are
checked at each OPEN
statement. If a file was dynamically allocated by a previous OPEN
statement and the
contents of the environment variable have changed since the previous
OPEN, then the
previous allocation is dynamically deallocated prior to dynamically
reallocating the
file using the options currently set in the environment variable."
Doesn't that include releasing the allocated, unused space?
"4.2.3.2 Environment variable contents for a QSAM file" does not
mention any specifics
about the release.
Results and examples of output
------------------------------
This is the result showing how much space the testfile has allocated
but not released.
Each record is 32 characters and the file contains 10 records. The 750
tracks
should be a much smaller number
Menu Options View Utilities Compilers
Help
------------------------------------------------------------------------------
DSLIST - Data Sets Matching P210.DEL1.T*
Row 1 of 1
Command ===> Scroll
===> CSR
Command - Enter "/" to select action Tracks %Used XT
Device
-------------------------------------------------------------------------------
P210.DEL1.TEST 750 1 1
3390
***************************** End of Data Set list
****************************
This is the result after issueing the FREE command on the file,
releasing the
unused but previously allocated space.
Menu Options View Utilities Compilers
Help
------------------------------------------------------------------------------
DSLIST - Data Sets Matching P210.DEL1.T* Free
completed
Command ===> Scroll
===> CSR
Command - Enter "/" to select action Tracks %Used
XT Device
-------------------------------------------------------------------------------
P210.DEL1.TEST 15 6
1 3390
***************************** End of Data Set list
****************************
This is the result after running the testprogram with the testfile
specifically
defined with DD-card and other attributes in the JCL:
//DYNAM DD DSN=P210.DEL1.TEST,
// DISP=(NEW,CATLG,KEEP),
// DCB=(RECFM=FB,LRECL=32),
// SPACE=(CYL,(50,10),RLSE)
DSLIST - Data Sets Matching P210.DEL1.TEST2
Row 1 of 1
Command ===> Scroll
===> CSR
Command - Enter "/" to select action Tracks %Used
XT Device
-------------------------------------------------------------------------------
P210.DEL1.TEST2 15 6
1 3390
***************************** End of Data Set list
****************************
The simple testprogram used to create the testfile with PUTENV and
directly with JCL
DD-card.
IDENTIFICATION DIVISION.
PROGRAM-ID. TESTALLC.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SOURCE-COMPUTER. IBM-370.
OBJECT-COMPUTER. IBM-370.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT TESTFILE ASSIGN DYNAM
FILE STATUS ST-DYNAMFILE.
I-O-CONTROL.
DATA DIVISION.
FILE SECTION.
FD TESTFILE
RECORDING MODE F.
01 TEST-RECORD PIC X(32).
WORKING-STORAGE SECTION.
01 WORK-AREA.
03 ST-DYNAMFILE PIC 9(2).
03 WS-TEST-RECORD PIC X(32).
01 SETENV-AREA.
03 SETENV-RC PIC S9(9) BINARY.
88 SETENV-RC-OK VALUE 0.
03 SETENV-POINTER POINTER.
03 SETENV-DATA PIC X(64).
*-----------------------------------------------------------------
PROCEDURE DIVISION.
*-----------------------------------------------------------------
INITIALIZE WORK-AREA
PERFORM SET-DYNAM-ENVAR
PERFORM WRITE-TEST-FILE
GOBACK.
*-----------------------------------------------------------------
SET-DYNAM-ENVAR SECTION.
*-----------------------------------------------------------------
INITIALIZE SETENV-AREA
STRING
'DYNAM=DSN(P210.DEL1.TEST) NEW CYL SPACE(50,10) KEEP'
X'00'
DELIMITED SIZE INTO SETENV-DATA
SET SETENV-POINTER TO ADDRESS OF SETENV-DATA
CALL 'PUTENV' USING BY VALUE SETENV-POINTER
RETURNING SETENV-RC
EVALUATE TRUE
WHEN SETENV-RC-OK
CONTINUE
WHEN OTHER
DISPLAY "PUTENV FAILED"
DISPLAY "RC=" SETENV-RC
GOBACK
END-EVALUATE
EXIT.
*-----------------------------------------------------------------
WRITE-TEST-FILE SECTION.
*-----------------------------------------------------------------
OPEN OUTPUT TESTFILE
DISPLAY 'OPEN FILESTATUS=' ST-DYNAMFILE
PERFORM 10 TIMES
MOVE FUNCTION CURRENT-DATE TO WS-TEST-RECORD
WRITE TEST-RECORD FROM WS-TEST-RECORD
DISPLAY 'WRITE FILESTATUS=' ST-DYNAMFILE
END-PERFORM
CLOSE TESTFILE
DISPLAY 'CLOSE FILESTATUS=' ST-DYNAMFILE
EXIT.
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