What is the differnce between UNIT and VOL Parameter in JCL?

[IT learner]

Hi,

Could anyone clearly explain me the difference between UNIT and VOL Parameter in JCL? Are not they just same?

[zprogrammer]

Unit and volume specify the location of a dataset.Unit specifies whether the dataset resides in DASD or TAPE
so you mention

UNIT=SYSDA or UNIT=TAPE

VOL specifies the volume seial number

Also here a very good link about the relationship

http://pic.dhe.ibm.com/infocenter/zos/v ... 560114.htm

[Robert Sample]

UNIT defines the type of device. VOL defines the actual tape or disk; this is important when a site may have hundreds of disk volumes and many thousands (even hundreds of thousands) of tape volumes. They are definitely NOT the same -- nowhere near it.

[IT learner]

Thanks Pandora.

Thanks Robert - your reply is pretty helpful to understand this. Many thanks.

[zprogrammer]

Glad it helped :-)