DD statement parameters - without SMS

DD statement parameters that can be used without modification are explained in Table 1. Parameters that should not be used or should be used only with caution are explained in Table 2.

VSAM has one DD statement parameter of its own, AMP. The AMP parameter takes effect when the data set defined by the DD statement is opened.

Table 1. Without SMS, DD Parameters to Use when Processing VSAM Data Sets
Parameter	Subparameter	Comment
AMP		This parameter has subparameters for: Overriding operands specified with the ACB, EXLST, or the GENCB macro instructions Supplying operands missing from the ACB or GENCB macro instruction Indicating checkpoint/restart options Indicating options when using ISAM macro instructions to process a key-sequenced data set Indicating that the data set is a VSAM data set when the DD statement specifies unit and volume information or DUMMY Indicating that VSAM is to supply storage dumps of the ACBs that identify the DD statement
DDNAME	ddname	No special considerations for VSAM.
DISP	SHR	Indicates that you are willing to share the data set with other jobs. This subparameter alone, however, does not guarantee that sharing will take place. See z/OS DFSMS Using Data Sets for a full description of data-set sharing.
DISP	OLD	No special considerations for VSAM.
DSNAME	dsname	Names the VSAM cluster to which the data set belongs.
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.
FREE		No special considerations for VSAM.
PROTECT		No special considerations for VSAM.
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.

Table 2. Without SMS, DD Parameters to Avoid when Processing VSAM Data Sets
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.
DISP	CATLG	VSAM data sets are cataloged and uncataloged as a result of an access method services command; if CATLG is coded, a message is issued, but the data set is not cataloged.
	DELETE	VSAM data sets are deleted as a result of an access method services command; if DELETE is coded, a message is issued, but the data set is not deleted.
	MOD	For VSAM data sets, MOD is treated as if OLD were specified.
	KEEP	Because KEEP is implied for VSAM data sets, it need not be coded.
	NEW	VSAM data spaces are initially allocated as a result of the access method services DEFINE command. If NEW is specified, the system allocates space, but it is never used by VSAM. Moreover, an access method services request for space may fail if the DISP=NEW acquisition of space causes too little space to remain available.
	UNCATLG	VSAM data sets are cataloged and uncataloged as a result of access method services commands; if UNCATLG is coded, a message is issued, but the data set is not uncataloged.
	PASS	Not applicable. However, because there is no error checking, coding PASS for a key-sequenced data set whose index resides on a like device does not result in an error. If a VSAM data set and its index reside on unlike devices, the results are unpredictable. In either case, the data set is not passed.
DLM		Not applicable.
DSNAME	dsname(area-name) dsname(generation) dsname(member)	VSAM uses the dsname. An area-name, generation number, or member name is ignored, if coded with the dsname.
	All temporary dsnames	Do not code a temporary dsname for a VSAM data set.
	All backward DD references of the form *ddname	Do not code backward references to VSAM data sets. If the object referred to is a cluster and the data set and index reside on unlike devices, the results of a backward DD reference are unpredictable.
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.
SPACE		VSAM data spaces are initially allocated as a result of the access method services DEFINE command. If SPACE is specified, the system allocates space, but it is never used by VSAM. Moreover, an access method services request for space may fail as a result of the SPACE acquisition of space.
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.