IDC2901I MASKING ENTRY NAME REQUIRES A KEYWORD MASK TO BE SPECIFIED

Explanation
A masking entry name that contained double asterisks
or percentage sign is specified in the DELETE command, and a MASK keyword was not specified along with the
command.  

System action
The DELETE command failed to
proceed. A return code of 8 was issued.

System programmer response
If the error recurs and the program
is not in error, look at the messages in the job log for more information.
Search problem reporting data bases for a fix for the problem. If
no fix exists, contact the IBM® Support
Center. Provide the JCL and the SYSOUT output for the job. 

Programmer response
You might perform one of the following procedures: Check the entry name. Correct it if it does not mean to be a masking
entry name, and reissue the command.
Specify MASK keyword to process the masking entry name, and reissue
the command.

Source
DFSMSdfp

Module
IDCDL01