A Global Directory file maps a region (a range of global variable names) to a segment (a file name or a file specified indirectly). GT.M utilities and the run-time system for GT.M processes use Global Directories to locate global data.
MUPIP CREATE uses Global Directories to define the specifications for creating database files. A Global Directory file:
Maps global variables and locks resource names to database files.
Provides configuration parameters for MUPIP CREATE to use when it creates and initializes Global Directories.
Typically, M programs using the same Global Directory share all of the same global variables. However, one can use the same Global Directory to map global variables to different files for different processes, by using environment variables in file names.
For example, two executing images share the same Global Directory file, and direct specified globals into the production database file. When the shared global directory maps a segment to a relative path or to an environment variable, each process may map to different files depending respectively on their process working directory or their definition of the environment variable.
An application can dynamically change a process to a different global directory. Executing processes can dynamically change global directories, or force a specific database access to use a specific Global Directory other than its current Global Directory.
Two global directories can map segments (either the same or different global variables) to the same database file.