The GXB is obtained once during system initialization by the server login exit. The exit returns a word to the server. This word is referred to as ‘the address of the GXB’, but the system initialization exit might store any value in the word. The address of the GXB is returned to the server in the parameter list and passed back to the installation-wide exits in each subsequent call. This block contains user installation-wide exit data that is needed to communicate with the server.

The GXB can contain an area to save the user data needed for all sessions. The usage of this block is determined by the exit. Access to the Global Exit Block must be controlled by the user-written installation-wide exits to ensure that updates are serialized and do not interfere with each other. This block is shared with the file security Installation-Wide Exit. The format of the GXB is entirely controlled by the login and file security installation-wide exits.