GDG
GDG:
GDG is a group of liked name datasets that are logically and chronologically related. A dataset in a GDG is called as generation.
Control cards:
DEFINE GDG (NAME (FACH01.GTP64.GDG) -
NOSCRATCH/SCRATCH -
NOEMPTY/EMPTY -
LIMIT (N))
LIMIT: maximum number of generations that can be in GDG catalog entry
EMPTY: When limit is exceed uncatalog all generations
NOEMPTY: when the limit exceed uncatalog old generation
SCRATCH: when the limit exceeds delete any uncatalog generations
NOSCRATCH: when the limit exceeds don’t delete any uncatalog generations
Maximum number of generations that we can catalog is 255
Maximum number of generations that we can create is 9999
RELATIVE DATASET NAME:
Relative dataset name is a common form used refers the generations of GDG relative to the current generation.
ABSOLUTE DATASET NAME:
Absolute dataset name is generation number used to refer the generation of a GDG.
GDG MODEL:
It is a model file used to supply the DCB attributes to the generations so that all the generations maintain same structure to increase the consistency.
The model must be in the same volume as the base GDG exists.
While creating GDG in multiple steps at the same time the generation numbers will not be updated till the end of job.
SYMBOLIC PARAMETERS
Symbolic parameters are variables in place of parameters in a procedure whose values can be changed while invoking the procedure.
Symbolic parameters can be preceded by & and can be of 8 characters long.
The values for the parameters can be supplied in the EXEC statement in which the procedure is invoked.
CONCATANATION
Concatenation is a method of combining two or more datasets and making them to behave as single file is called as concatenation.
To concatenate the datasets we should not code the name of DD statements, only the first dataset contains the DD name
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