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> ## Updating Multiple Databases

> The J2EE transaction manager controls all enterprise bean transactions except for bean-managed JDBC transactions. The J2EE transaction manager allows an enterprise bean to update multiple databases within a transaction. The figures that follow show two scenarios for updating multiple databases in a single transaction.

> In Figure 30-2, 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.

> Figure 30-2 Updating Multiple Databases

> In Figure 30-3, 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 J2EE server. The method in `Bean-B` updates Database Y. The transaction managers of the J2EE servers ensure that both databases are updated in the same transaction.

> Figure 30-3 Updating Multiple Databases across J2EE Servers

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