InterSystems FAQ rubric
Temporary globals stored in the IRISTEMP/CACHETEMP databases are used when a process does not need to store data indefinitely, but requires the powerful performance of globals. The IRISTEMP/CACHETEMP databases are not journaled, so using temporary globals does not create journal files.
The system uses the IRISTEMP/CACHETEMP databases for temporary storage and are available to users for the same.