Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Updating Multiple Databases

The Java EE transaction manager controls all enterprise bean transactions except for bean-managed JDBC transactions. The Java EE transaction manager allows an enterprise bean to update multiple databases within a transaction. Figure 54-2 and Figure 54-3 show two scenarios for updating multiple databases in a single transaction.

In Figure 54-2, the client invokes a business method in `Bean-A`. The business method begins a transaction, updates Database X, updates Database Y, and invokes a business method in `Bean-B`. The second business method updates Database Z and returns control to the business method in `Bean-A`, which commits the transaction. All three database updates occur in the same transaction.

In Figure 54-3, the client calls a business method in `Bean-A`, which begins a transaction and updates Database X. Then `Bean-A` invokes a method in `Bean-B`, which resides in a remote Java EE server. The method in `Bean-B` updates Database Y. The transaction managers of the Java EE servers ensure that both databases are updated in the same transaction.

Figure 54-2 Updating Multiple Databases

Figure 54-3 Updating Multiple Databases Across Java EE Servers

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