Maximum Number of Namespaces and Databases

InterSystems FAQ rubric

The maximum number of namespaces that can be created in one instance is 2047. However, to use a large number of namespaces, you will need to configure memory accordingly.

The maximum number of databases (including remote databases) that can be created in one instance is 15998. Depending on the type of license, there may be restrictions on the number that can be created. For details, please refer to the following document.
Database Configuration [IRIS]
Database Configuration