Using BLP processing to read data on a volser and receiving :
Release : 14.0
Component : CA 1 Tape Management
BLP processing is the same as NL processing except that CA 1 Tape Management System processes any file sequence as a file sequence of 1 with BLP. The input data set name validity check as described for SL processing is performed. The data set name found in the TMC record for the volume and the DSN specified in the DD statement are used.
You can either can either code the dsname in the JCL or code
EXPDT=98000 to bypass CA-1 control.
The following link has more details on this :