What is the purpose of $RMSYMSB?
$RMSYMSB is a global variable introduced by fix RO97849 or RO97747 or RO97748 to address a problem with system symbols substitution.
It contains a prefix character identifying a symbol in the variable name following the prefix.
The system symbols are created at the time the region is initialized using D SYMBOLS system command.
Some symbols are:
If any resource is defined with a matching symbol then it will be substituted.
For example, if D J,_HOSTNAME is set as system command in a display and heartbeat details, then it will be executed as D J,hostname_value.
By defaut, '_' prefix is used if $RMSYMSB is not set. If it is set, then this one should be replaced the '_' in the system command from the display resource definition.