To tell what type of security is set up for a Librarian master file run an INDEX report against that specific master file. It will show what security is setup, MCD, External.
It will also show what options were set when the Librarian Master File was initialized.
Here is an example of running the INDEX report.
//STEP1 EXEC PGM=AFOLIBR,PARM='NJTA,NRJS'
//STEPLIB DD DSN=LIBSYS.LIBR.V44.LVL1.CALJLINK,DISP=SHR
//INDEX DD SYSOUT=*
//MASTER DD DSN=YOUR.MASTER.FILE,DISP=SHR
//SYSPRINT DD SYSOUT=*
//OSJOB DD DUMMY
//SYSIN DD *
THE MASTER FILE DEFAULTS FOR 'YOUR.MASTER.FILE' ARE:
ARCHIVED AT 5 LEVELS YESBYPP YESGPO SEP
PR NOVAR NOEXEC NOLIST
NOPUNCH COMPRESS=FULL RESEQ YESSEQUPD
SECURITY: EXTERNAL SEQ=/73,8,100,100/ NO I/P EXIT REQ NO O/P EXIT REQUIRED