A global variable is a named memory variable that is retrieved or modified through SQL statements.
Global variables enable applications to share relational data among SQL statements, without the need for additional application logic to support this data transfer.
A global variable is defined within a schema. A global variable defined in a module within a schema is referred to as a module global variable. All other global variables are referred to as schema global variables.
The definitions for global variables are recorded in the system catalogs.