Module 3: Access Method Services (AMS)
- What is RSDS? Please refer complete information here
- RRDS cluster can be defined using DEFINE CLUSTER command which is explained along with Syntax in ‘IDCAMS DEFINE CLUSTER Command’ section.
- Defining RRDS is identical to defining an ESDS. This is because RRDS also has only data component and does not contain Primary key.
- Below is the most basic Syntax for defining RRDS cluster:-
DEFINE CLUSTER - ( NAME(rrds-file-name) - CYLINDERS ( primary[ secondary] ) - VOLUMES ( volser1 [volser2...] ) - [CONTROLINTERVALSIZE ( size ) ] - NUMBERED - [RECORDSIZE ( average maximum ) ] ) - [ DATA - ([NAME(rrds-file-name.DATA)]) ]
- Meaning of each of above parameters and other few more parameters(which are not included in above Simplified Syntax) can be referred in ‘IDCAMS- DEFINE CLUSTER command’ Section
- NUMBERED parameter must be coded in DEFINE CLUSTER command to instruct VSAM that the cluster is RRDS.
- Since RRDS does not have key field, Parameters related to key fields are not coded when defining ESDS cluster
- RRDS contains only fixed length records. Thus, make sure RECORDSIZE must contain same average and maximum record length
- RRDS has only DATA component and thus INDEX component is not coded for RRDS cluster
- FREESPACE parameter is not required either, since an RRDS has no embedded free space between records
- Below JCL example depicts the creation of RRDS cluster:-
//DEPTJOB JOB A123,’STEVE’ //RRDSDFN EXEC PGM=IDCAMS //SYSPRINT DD SYSOUT=* //SYSIN DD * DEFINE CLUSTER(NAME(PAYT.PAYROLL.PRCSRRDS.MSTR) - CYLINDERS ( 5 1 ) - VOLUME(VSMP91) - CONTROLINTERVALSIZE(4096) - NUMBERED - RECORDSIZE(250 250) ) - DATA( - NAME(PAYT.PAYROLL.PRCSRRDS.MSTR.DATA)) /*
- Description: - Above job will create VSAM RRDS cluster since NUMBERED is specified as type of cluster. It will be created with name ‘PAYT.PAYROLL.PRCSRRDS.MSTR’ along with DATA component having name ‘PAYT.PAYROLL.PRCSRRDS.MSTR.DATA’. This cluster will be created on volume ‘ VSMP91’. 5 cylinders of primary and 1 cylinders of secondary space will be allocated. The size of control interval specified is 4096 bytes. Average and maximum records length specified as 250 bytes each which indicates, RRDS contains fixed length records