IMS Installation Defaults module (DFSIDEF0)

You can use the DFSIDEF0 module to define options for database recovery control (DBRC). You can also use the module to define supervisor call instruction (SVC) numbers that are reserved for use by the generated IMS system.

The DFSIDEF0 module is provided in the IMS.ADFSSMPL data set.

You are not required to use the DFSIDEF0 module. If you do not use the module, or if the module cannot be loaded at initialization time, and the keywords are not specified as IMS execution parameters, IMS default values are used instead.

If you use the DFSIDEF0 module, ensure that the DFSIDEF0 module resides in an APF-authorized library that is included in the IMS Control Region JOBLIB or STEPLIB concatenation, or in the z/OS® LINKLIST concatenation.

If you use the DFSIDEF0 module, ensure that you assemble and link the DFSIDEF0 module into the IMS.SDFSRESL data set. The following sample JCL assembles and binds the DFSIDEF0 module into the IMS.SDFSRESL data set:

//ASSEMBLE EXEC PGM=ASMA90,PARM='NOOBJ,DECK'
//SYSLIB DD DSN=IMS.SDFSMAC,DISP=SHR
//SYSPUNCH DD DISP=OLD,DSN=IMS.OBJDSET(DFSIDEF0)
//SYSPRINT DD SYSOUT=*
//SYSUT1   DD UNIT=SYSDA,DISP=(,DELETE),SPACE=(CYL,(15,15))
//SYSIN    DD *
IDEF0    TITLE 'DFSIDEF0 - IMS INSTALLATION DEFAULTS BLOCK'
DFSIDEF0 CSECT
         SPACE 1
         DFSIDEF TYPE=BEGIN
         DFSIDEF TYPE=PARM,DBRC=YES
*****    DFSIDEF TYPE=PARM,DBRC=NO
*****    DFSIDEF TYPE=PARM,DBRC=FORCE
*
*****    DFSIDEF TYPE=PARM,SVC2=254 
*****    DFSIDEF TYPE=PARM,SVC4=255
         DFSIDEF TYPE=END
         END   DFSIDEF0
//STEP1 EXEC PGM=IEWL,
//             PARM='SIZE=(880K,64K),NCAL,LET,REUS,XREF,LIST'
//SYSPRINT DD  SYSOUT=*
//SYSPUNCH DD DSN=IMS.OBJDSET,DISP=SHR
//SYSLMOD  DD DSN=IMS.SDFSRESL,DISP=SHR
//SYSUT1   DD UNIT=(SYSDA,SEP=(SYSLMOD,SYSPUNCH)),SPACE=(CYL,(10,1))
//SYSLIN   DD *
 INCLUDE SYSPUNCH(DFSIDEF0)
 NAME DFSIDEF0(R)

If you specify RMODE, you must specify RMODE=24 and AMODE=24.

DFSIDEF macro keywords in DFSIDEF0

You can specify the following parameters on the DFSIDEF macro in the DFSIDEF0 module:

DBRC=

Species whether DBRC is to be used during this execution of IMS for batch and utility environments. The default value is YES. The DBRC= parameter that is specified in the DFSIDEF0 module is valid only for batch and utility environments and is ignored for all other system environments.

If DBRC=Y or DBRC=N is specified on the DFSIDEF macro, the DBRC= value that is specified on the DFSIDEF macro is overridden by the DBRC= value that is specified in the DFSPBxxx member of the IMS PROCLIB data set. To do this, you must define the RGSUF= parameter in your DLIBATCH or DBBBATCH procedure. In the DFSPBxxx member, you can specify only DBRC=N or DBRC=Y.

YES

DBRC is used during this execution of IMS.

NO

DBRC is not used during this execution of IMS.

FORCE

DBRC is always used during this execution of IMS, unless this is a batch backout execution of IMS.

If this is a batch backout execution of IMS, the DBRC=FORCE specification defined in DFSIDEF0 can be overridden by specifying DBRC=NO on the EXEC procedure. Thus, if the previous execution of IMS used DBRC but not IRLM, batch backout executes without DBRC.

SVC2=

The type 2 SVC number that IMS uses. You can specify a value in the range 200 - 255 for this parameter. The SVC2= parameter that is specified on the DFSIDEF macro is valid for all IMS environments.

The SVC2= value that is specified on the DFSIDEF macro is overridden by the value that is specified in the DFSPBxxx member or in JCL.

If the SVC2= parameter is not defined on the DFSIDEF macro or as an IMS execution parameter, IMS uses a default value of 254.

To generate sample JCL for relinking the type 2 SVC routine, DFSVC200, as IGCxxx, where xxx is the type 2 SVC number, specify TYPE=GEN,SVC2=xxx on the DFSIDEF macro.

SVC4=

The type 4 SVC number that IMS uses for DBRC environments. You can specify a value in the range 200 - 255 for this parameter.

If the SVC4= parameter is not defined in the DFSIDEF0 module, IMS uses a default value of 255.

To generate sample JCL for relinking the type 4 SVC routine, DSP00MVS, as IGC00yyy, where yyy is the EBCDIC representation of the zoned-decimal type 4 value, specify TYPE=GEN,SVC4=zzz on the DFSIDEF macro.