The DD statement parameters that you should use for VSAM data sets are shown in Table 1. You can also use other DD parameters, if needed, to override attributes in the data class (such as KEYLEN and KEYOFF). Parameters that should not be used or should be used only with caution are explained in Table 2.
| Parameter | Subparameter | Comment |
|---|---|---|
| AMP | This parameter has subparameters for:
|
|
| DATACLAS | data-class-name | No special considerations for VSAM data sets, except that the record organization (RECORG) should specify a VSAM data set. |
| DDNAME | ddname | No special considerations for VSAM data sets. |
| DISP | all subparameters | All DISP subparameters can be used for VSAM data sets except UNCATLG, which is ignored (KEEP is implied if UNCATLG is coded). |
| DSNAME | dsname | VSAM uses the dsname. An area-name (area-name), generation number (generation), or member name (member) is ignored if coded with dsname. |
| All temporary dsnames | You can code a temporary dsname for a VSAM data set. | |
| All backward DD references of the form *.ddname | You can code backward references to VSAM data sets on the REFDD parameter. | |
| DUMMY | No special considerations for VSAM, except that an attempt to read results in an end-of-data condition, and an attempt to write results in a return code that indicates the write was successful. If specified, AMP=AMORG must also be specified. | |
| DYNAM | No special considerations for VSAM data sets. | |
| FREE | No special considerations for VSAM data sets. | |
| MGMTCLAS | mgmt-class-name | No special considerations for VSAM data sets. |
| RECORG | KS | Specifies a key-sequenced data set. |
| ES | Specifies an entry-sequenced data set. | |
| RR | Specifies a relative record data set. | |
| LS | Specifies a linear space data set. | |
| RECORG overrides the record organization in the data class. | ||
| SECMODEL | No special considerations for VSAM data sets. | |
| SPACE | No special considerations for VSAM data sets. | |
| STORCLAS | storage-class-name | No special considerations for VSAM data sets. If a storage class is assigned, the VSAM data set is managed by SMS. |
| UNIT | device number | You cannot use a device number with an SMS-managed data set. |
| type | If the data set is SMS-managed, the unit type is unimportant. | |
| group | Must be a group supported by VSAM. If not, OPEN will fail. | |
| p | System must have enough units to mount all of the volumes specified. If sufficient units are available, UNIT=P can improve performance by avoiding the mounting and demounting of volumes. For multivolume data sets defined in catalogs, UNIT=(,P) must be specified because all primary volumes must be mounted in parallel. | |
| unit count | If the number of devices requested is greater than the number of volumes on which the data set resides, the extra devices are allocated anyway. If a key-sequenced data set and its index reside on unlike devices, the extra devices are allocated evenly between the unlike device types. If the number of devices requested is less than the number of volumes on which the data set resides but greater than the minimum number required to gain access to the data set, the devices over the minimum are allocated evenly between unlike device types. If devices beyond the count specified are in use by another task but can be shared and have mounted on them volumes containing parts of the data set to be processed, they will also be allocated to this data set. | |
| DEFER | No special considerations for VSAM. | |
| VOLUME | PRIVATE SER |
No special considerations for VSAM. The volume serial number(s) used in the access method services DEFINE command for the data set must match the volume serial numbers in the VOLUME=SER specification when the data set is defined. After a VSAM data set is defined, the volume serial number(s) need not be specified on a DD statement to retrieve the data set. If, however, VOLUME=SER and UNIT=type are specified, only those volumes specifically named are initially mounted. Other volumes may be mounted when needed, if at least one of the units allocated to the data set cannot be shared or the unit count is equal to the total number of volumes allocated to the data set. A unit cannot be shared when the unit count is less than the number of volume serial numbers specified or when DEFER is specified. |
| Parameter | Subparameter | Comment |
|---|---|---|
| BURST | Not applicable. | |
| CHARS | Not applicable. | |
| CHKPT | VSAM ignores CHKPT. | |
| COPIES | Not applicable. | |
| DATA | Not applicable. | |
| DCB | All | Not applicable. |
| DEST | Specify DEST only with the SYSOUT parameter. | |
| DLM | Not applicable. | |
| FCB | Not applicable. | |
| FLASH | Not applicable. | |
| LABEL | BLP, NL, NSL | Not applicable |
| IN | Not applicable | |
| OUT | Not applicable | |
| NOPWREAD | The password-protection bit is set for all VSAM data sets, regardless of the PASSWORD/NOPWREAD specification in the LABEL parameter. | |
| PASSWORD | The password-protection bit is set for all VSAM data sets, regardless of the PASSWORD/NOPWREAD specification in the LABEL parameter. | |
| SL, SUL | Although these parameters apply to direct-access storage devices, SL is always used for VSAM, whether you specify SL, SUL, or neither. | |
| MODIFY | Not applicable. | |
| SYSOUT | If SYSOUT is coded with a mutually exclusive parameter (for example, DISP), the job step is terminated with an error message. | |
| UCS | All | Not applicable. |
| UNIT | AFF | Use this subparameter carefully. If the cluster components, the data and its index, reside on unlike devices, the results of UNIT=AFF are unpredictable. |
| VOLUME | REF | Use this subparameter carefully. If the referenced volumes are not a subset of those contained in the catalog record for the data set, the results are unpredictable. |
| vol-seq-number | Results are unpredictable. | |
| volume-count | Not applicable because this subparameter gives the number of nonspecific volumes. All VSAM volumes must be specifically defined. | |
| * | Not applicable. |