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Lesson 12

Distributed Database Conclusion

This module covered the important new features of distributed databases in the Oracle environment.
In this module, you learned how to:
  1. List primary Oracle enhancements for distributed databases
  2. Work with queue propagation
  3. Create primary key snapshots in replication
  4. Identify the new Oracle features for updateable snapshots
  5. Use deferred constraints on updateable snapshots
  6. Describe enhanced LOB support in Oracle
  7. Monitor replication by querying V$ views
  8. Implement snapshot security
  9. Walk through the steps for creating snapshots offline
  10. Identify the new features of snapshot deployment templates

Queue-to-Queue Propagations

A propagation can be queue-to-queue or queue-to-database link (queue-to-dblink). A queue-to-queue propagation always has its own exclusive propagation job to propagate messages from the source queue to the destination queue. Because each propagation job has its own propagation schedule, the propagation schedule of each queue-to-queue propagation can be managed separately. Even when multiple queue-to-queue propagations use the same database link, you can enable, disable, or set the propagation schedule for each queue-to-queue propagation separately.
A single database link can be used by multiple queue-to-queue propagations. The database link must be created with the service name specified as the global name of the database that contains the destination queue. In contrast, a queue-to-dblink propagation shares a propagation job with other queue-to-dblink propagations from the same source queue that use the same database link. Therefore, these propagations share the same propagation schedule, and any change to the propagation schedule affects all of the queue-to-dblink propagations from the same source queue that use the database link.

Glossary
The following terms were defined in this module:
  1. Advanced Queuing (AQ): A utility to store transactions in a queue, distribute the queue to other databases, and then retrieve and run the queued transactions.
  2. Deployment template: A set of commands that create one or more snapshots at a remote site. The template can be used repeatedly to create identical sets of snapshots at multiple remote sites.
  3. Instantiate: To create a specific version of an object (such as a snapshot) based on a template and some specific variables.
  4. Multimaster replication: Advanced replication features allowing updates on tables in remote sites as if every site were the master site.
  5. Offline instantiation: Creating snapshot templates using export and import utilities. No connection is required between the master and the remote site during the process.
  6. Online instantiation: Creating snapshot templates in real time with a connection between the master and the remote sites.
  7. Primary key snapshot: A copy of a table or view. Changed rows are refreshed by retrieving the row using its primary key value.
  8. ROWID snapshot: A copy of a table. Changed rows are refreshed by retrieving the row using its ROWID.
  9. Trusted: A security model in which an administrator has access privileges to local and remote sites.
  10. Untrusted: A security model in which an administrator has access privileges only to the local site.
  11. Updateable snapshot: A snapshot that supports insert, update, and delete on the remote site.
We are now ready to look at the new features of Oracle Parallel Server (OPS), and see how OPS has been enhanced in Oracle.
In the next module, you will learn about new features for partitioned tables.