This Appendix briefly describes the new replication features of the Oracle8i Server and provides pointers to other chapters in this document where you can get additional information. This chapter also retains Oracle8 Server new features to help those users migrating from Oracle7 to Oracle8i.
New features include:
The Oracle8 features and enhancements described below comprise the overall effort to optimize multimaster replication performance and make certain types of snapshot subsetting fast refreshable. LOB support was added for Oracle8. The manageability and security was also enhanced for Oracle8. All are included in advanced replication.
Oracle8 provides significant performance improvements based on the following new features.
Dramatically improves throughput performance by parallelizing the propagation of a replication transaction stream while maintaining consistency and transaction dependencies.
Additional Information: See "Deciding between Serial and Parallel Propagation".
Additional Information: See "Oracle's Multimaster Replication Architecture".
Oracle8 reduces the amount of replicated data propagated over the network. Propagation can be reduced to only the following: new values of columns updated; old values of columns needed for conflict detection and resolution; and primary key values. This feature is important for performance when replicating LOBs.
Additional Information: See "Minimizing Data Propagation for Update Conflict Resolution".
Snapshots defined with certain types of subqueries can now be fast refreshed. This enables subsets of data to be easily defined and maintained. This feature is important for mass deployment applications, such as salesforce automation and branch automation.
Additional Information: See "Data Subsetting with Snapshots".
Oracle8 supports the replication of the following types of large objects:
Additional Information: See the following sections: "Datatype Considerations for Replicated Tables" and "Datatype Considerations for Snapshots".
Oracle8 facilitates database management with the following features.
Replication master groups can now be individually quiesced without impacting other replication groups. Master groups can continue to replication updates while other master groups are quiesced.
Additional Information: See "Suspending Replication Activity for a Master Group".
Primary key snapshots allow you to reorganize master tables while preserving fast refresh capability. Oracle8 adds primary key snapshots as the default, and continues to support ROWID snapshots.
Additional Information: See Appendix B, "Migration and Compatibility".
Oracle8 automatically registers information about a snapshot s at master sites. This facilitates monitoring and distributed administration.
Additional Information: See "Registering a Snapshot at its Master Site".
Oracle8 provides utilities to enable you to "reorg" master tables while preserving the consistency of master snapshot logs.
Additional Information: See "Reorganizing Master Tables that Have Snapshot Logs".
Offline instantiation of schemas and database using Export/Import is now more automatic.
Additional Information: See "Snapshot Cloning and Offline Instantiation".
Updateable snapshots now support declarative referential and uniqueness constraints.
Additional Information: See "Replicating Object Definitions to Master Sites".
Oracle8 supports the replication of partitioned tables and indexes. You can use this feature if you want the replicated table to have the same partitions as the table at the master definition site.
Oracle8 system-based security model:
Additional Information: See "Preparing for Multimaster Replication", "Prepare for Snapshots", and Appendix B, "Migration and Compatibility".
Replication Manager now includes several wizards to help you configure your system quickly.
Oracle Replication Manager includes support for most new features of Oracle8 Server replication functionality, including:
The Oracle8i features and enhancements described below comprise the overall effort to optimize replication performance and make snapshot environment distribution and security more effective. All are included in advanced replication.
Significant performance gains are realized by the internalization of PL/SQL replication packages and by optimizations to snapshot refresh.
Continuing the trend started with Oracle8, more replication code has been moved into the database engine in Oracle8i. The PL/SQL generated packages used to apply replicated transactions at a remote site have been internalized. This allows replicated transactions to be more efficiently applied at remote sites and because packages are not generated, a site can be more quickly instantiated. Internal packages are also more secure because they are tamper proof.
Snapshot refresh has been optimized to support large refresh groups. There is improved support for subquery snapshots, and for null refresh (no changes to the master tables since the last refresh). A single refresh group can now contain 400 snapshots, and the number of roundtrips required to refresh snapshots in a refresh group has been reduced.
With Oracle8i, Oracle is shifting its advanced replication focus from back office types of applications requiring near real-time replication of data to the growing market of front office applications, in particular mass deployment.
These facilitate the mass deployment of information to support such applications as field service and sales force automation. These templates represent a grouping together of snapshots and other database objects to be instantiated at a node. They allow a DBA to centrally package a snapshot environment for easy, custom, and secure distribution to one or multiple sites. The goal is to create the environment once, then deploy the snapshot deployment template as often as necessary. Template parameters allow data subsetting at a remote site without redefining the template, and a template may be defined as public or private. Public templates may be instantiated at any site, whereas private ones can only be instantiated at pre-defined, authorized sites. An Oracle Replication Manager deployment wizard guides the DBA through the selection of schema objects to add to the template, the selection of parameters, and defining authorizations.
Updateable snapshots can now be subsetted horizontally (selected rows) or vertically (selected columns). The previous release allows horizontal subsetting only. Vertical partitioning allows the deployment of the minimum amount of data needed by a remote site, thus reducing connection time. It also protects snapshot sites from changes to their associated masters. A column can be added to a master site without impacting the snapshot site, or a column can be deleted and not impact the snapshot site, if the snapshot site does not currently reference that column.
Snapshot deployment templates can be instantiated online or offline. Online instantiation allows a snapshot site to instantiate the template while connected to the target master site. The advantage here is that the data will be current. However, this is at the cost of requiring a live connection, possibly of long duration and having the potential of generating extreme network traffic that could degrade other network services. Offline instantiation allows the DBA to package the deployment group templates and required data onto some type of storage media (tape, CD-ROM, etc.) for distribution to a snapshot site. Instead of connecting to the master site, instantiation can be done by pulling the template and data from the storage media. Users can fast refresh immediately after completing an offline instantiation, a full refresh is not required. Offline instantiation is an ideal solution for mass deployment situations where many disconnected laptops will be instantiating the target template.
While the scripts used to instantiate a snapshot site are generated at the master site and can control access to data, it is still necessary to connect to a receiver and proxy snapshot administrator to propagate replicated transactions and to refresh snap-shots. Oracle8i enhancements to the replication security model eliminate certain security deficiencies regarding the granting of privileges to untrusted sites.
A number of improvements have been made to the Oracle Replication Manager, some have already been mentioned. A major and noticeable enhancement is that it has been rewritten to conform to the new Oracle Enterprise Manager (OEM) Java interface. Oracle Replication Manager can now be run from anywhere in the network, and it is not constrained to a Windows based machine. There is also a replication class of events in OEM which, for example, can be used to monitor errors or delinquent snapshot refreshes.
The integration between the Oracle8i Server/Oracle8i Server Enterprise Edition and Oracle8i Lite has been improved to provide better performance and increased functionality. All of the replication changes previously described are supported and Oracle Lite users with laptops at remote sites will especially benefit from reduced connection time.