You can only change the document storage type for a publishable document type if you own the lock on the IS document type (or you have it checked out) and you have write permission to the IS document type.

For documents published to the Broker, the storage type assigned to a document can be overridden by the storage type assigned to the client queue on the Broker.

Changing a webMethods Messaging property may cause the publishable document type to be out of sync with the associated provider definition. For information about synchronizing document types, see About Synchronizing Publishable Document Types.