Mapping macros map the parameter options in many callable services. The fields with the comment "Reserved for IBM® Use" are not programming interfaces. A complete list of the options for each macro is listed in the macro in Macros mapping parameter options.
Most of the mapping macros can be expanded with or without a DSECT statement. The invocation operand DSECT=YES (default) can be used with either reentrant or nonreentrant programs with the appropriate rules governing the storage backed by the USING statement.
Many of the mapping macros exploit the fact that DC expands as a DS in a DSECT and as a DC with its initialized value in a CSECT. When these fields are expanded as or within DSECTs, the program is responsible for initializing the necessary fields.