         << LINES .001/.009 ARE RESERVED FOR SYSTEMS INTEGRATION >>     00000001
 +--+--+--+--+--+--+--+--+--+--------------------+             <<01461>>00365000
 |LK|/////|            XDD head index            |4            <<01461>>00370000
 +--+-----+--------------------------------------+             <<01461>>00375000
  Word 4.(0:1) -- Auxiliary lock mechanism.  If set, device is <<01461>>00575100
                  being deallocated but LDT and XDD are incon- <<01461>>00575200
                  sistent and their SIRs are  released.  ALLO- <<01461>>00575300
                  CATE  co-operates by rejecting access to de- <<01461>>00575400
                  vice.                                        <<01461>>00575500
       LDT'IO'2'CONCURRENT= 5                       #,                  00841000
   LDT'LOCKED             = LDT(LDT'INDEX+4).( 0:1) #,         <<01461>>01006000
   LDTX'ALTER'PIN          = LDTX(LDTX'INDEX+3)       #,                02366000
