Bypassing Label processing for tape datasets

Bypass Label Processing (BLP) is a method of accessing tapes or cartridges. Use of BLP is usually restricted, requiring RACF authority, because great care is required. 

BLP is often used if the dataset name or volume serial is not known, such as when recieving a tape from an external organization.

To specify that you want to read a tape or cartridge using BLP, you should specify BLP in the LABEL parameter of the DD statement. 

LABEL=(2,BLP) specifies you want to read the second file on the tape/cartridge. Note that any Headers and Trailers on the tape/cartridge are treated as being files. 

Any tape format can be read using BLP, from Standard Label to No Label.

To calculate the file number use the following formula:

x=3y - 1

where x is the number to be used with BLP (ie LABEL=(x,BLP) ), and y is the number of the file (excluding headers, trailers,etc) that you want to access (ie the file number you would use for standard labels (SL) ), so if you want to access the first file on a tape (with headers & trailers) x would be (3*1) - 1 , So you would code LABEL=(2,BLP). The second file would be accessed using LABEL=(5,BLP). (Remember there will be headers and trailers for each file). 

To access the Header record code LABEL=(,BLP)   

 No dataset name or volume serial number validation is done with BLP so your DSN name and VOL=SER can be set to any value.

When you run your job with BLP a message will appear on the Operator Console requesting the Volume Serial Number. Once the VOLSER is entered at the console the job step will start and the tape is processed.