This command macro is used to check if a subfile is open and if opened returns the SW00SR slot base address
Mandatory Parameters for DBIFB
REF= (Refname|Label|A/label|FIRST|NEXT)
FIRST : Gets the SW00SR slot address in R3 of the first opened subfile
NEXT : Subfile opened next to the current subfile
Both FIRST and NEXT return with R14 pointing to 8-Byte location of the REF name
Optional Parameters for DBIFB
ERROR|ERRORA
NEWREF
NEWREF : Allows to change Refname if located
REG=
EXAMPLE:
DBIFB REF=WRMBSQ
#IF (R3,NZ)
DBCLS REF=WRMBSQ
#EIF
