ADRSUB is the DDNAME for the Internal Reader (IRDR) and is only used with CA Ideal and CA Dataquery. The definition for (IRDR) in supplied in member VQ14CSD in the CAVQSAMP library for CA IPC r14 and VQ15CSD, for CA IPC r15. A site can have this dynamically allocated if they choose.
To Verify if the IRDR entry is defined under CICS you may enter commands :
CEDA (CEDC or CEDB) VIEW TDQUEUE(IRDR) GROUP(*) or CEMT INQUIR TDQUEUE(IRDR)