This command will show interactive screen when you can manipulate with actual media in library.
Option 1 allow you add particular media into BRMS and initialize it.
WRKMLMBRM MLB(TS4300_BCK) VOL(AS0001)
Work with Media Library Media SYSTEM1
Media library . . . . . . : TS4300_BCK
Position to . . . . . . . . Starting characters
Type options, press Enter.
1=Add MLB media 2=Work with media 5=Initialize
6=Change category 7=Eject 8=Mount 9=Demount
Media --BRM Information--
Opt Volume Type Category Status Media Class Status
AS0001 M8 *SHARE400 Available TTC_SHORT *EXP
Bottom
F3=Exit F5=Refresh F9=System command F12=Cancel F13=Repeat