Prerequisites

RED Initialization Parameters for CICS

You must set the following CICS System Initialization Parameters for Substation ES to connect to a CICS Region: 
PLTPI=RI
PLTSD=RD

Review USERHLQ.ASM(SXXACFGC), which contains the parameters that can be used to configure the RED interface. You might not have to make changes to it.
Note: RED transactions (#RED) use CICS OTE. Review your MAXOPENTCB parameter to ensure it is greater than the transaction interface for RED parameter CICS-MAIN-MAX which defaults to 21.