Shared memory is the area of the working memory that is used by multiple processes of a database.
The DBM server of a database can consist of multiple processes. These processes communicate via shared memory. This communication is necessary in the following situations:
To coordinate access to shared resources, such as the parameter file or the DBM server log file.
To transfer database parameters.
To retrieve the results of special DBM server processes, such as the Command Scheduler.
The database system also saves the content of the DBM server's shared memory in the files. This ensures that the contents of the shared memory are also available even when no DBM server processes are active.
More information: Database Administration, Miscellaneous Database Files
DBM server processes from different databases cannot communicate with one another via shared memory.
Database Manager CLI, Other Commands for Managing Database Manager