Understand PI MDB to PI AF migration and synchronization

On PI Server 2010 and later versions, the Data Archive server maintains a two-way synchronization between PI MDB and PI AF. Changes that you make in PI MDB are automatically reflected in PI AF. Similarly, changes that you make in PI AF are automatically reflected in PI MDB. This means that PI AF-based applications and PI MDB-based applications can access the same content.

On PI Server 2010 and later versions, PI AF is the system of record. When AF Link cannot connect to the PI AF server, PI MDB becomes read-only. Users can continue to make changes in PI AF, but cannot edit PI MDB until the connection is restored.

PI MDB and PI AF synchronization begins with an initial migration and is thereafter automatic. Migration is the process during which the Data Archive server initially copies the PI Module Database to a PI AF database. Migration is typically a one-time operation, but it is possible to re-migrate if necessary.

During the initial installation of or upgrade to PI Server 2010 or later versions, you must choose whether to enable PI MDB during setup. If you do not choose to enable PI MDB, then migration and synchronization do not occur and PI MDB is thereafter read-only. To enable PI MDB at any point after installation, you must manually initiate a migration.

Limitations on the synchronization process

AF elements that have names starting with a non-alphanumeric character cannot be synchronized with the Module Database. To maintain MDB to AF synchronization, avoid creating names like this. If MDB loses synchronization with AF due to an element that has a name starting with a non-alphanumeric character, you must either rename the element or delete the element and reset MDB.

If AF Link subsystem is configured to run as, for example, User1, and that same user makes changes to AF elements, those changes might not synchronize with MDB.

• If the change made in PI AF is either adding or deleting an element, that change will be synchronized.

• If the change is anything else, such as an edit, the change is filtered out by AF Link subsystem because it assumes the change was made by itself. AF Link modifies PI AF only if there is a change in MDB and therefore all changes made by itself are not synchronized back to MDB.