This is explained in DocOps Section Concurrently Updating the PROTSYM File:
The application uses the MVS RESERVE and DEQ macros to allow sharing of the PROTSYM file between regions or systems. The resource major name used in the RESERVE and DEQ macros is INTERTST. Place the major name INTERTST into an MVS service that converts the RESERVE into a cross-system ENQ if this service is available at your site.
Use GRS to convert the RESERVE to a global (SYSTEMS) ENQ.
The major name is INTERTST and the minor name is the data set name of the PROTSYM file.
Code the following generic GRS conversion in the GRSRNLxx parmlib member:
RNLDEF RNL(CON) TYPE(GENERIC) QNAME(INTERTST)