Release 2 (8.1.6)
Part Number A76959-01
This appendix briefly describes the new replication features of Oracle8i and provides pointers to where you can get additional information. This chapter also retains Oracle8 (release 8.0) new features to help those users migrating from Oracle7 to Oracle8i (release 8.1).
New features include:
The Oracle8i (release 8.1) replication features and enhancements described below comprise the overall effort to optimize replication performance and make snapshot environment distribution and security more effective.
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 has improved replication support for the growing market of front office applications, in particular mass deployment.
Deployment templates 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, and then deploy the 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 Template Wizard guides the DBA through the selection of schema objects to add to the template, the selection of parameters, and defining authorizations. Deployment templates can be used to create snapshot environments at the following types of snapshot sites: Oracle8i Enterprise Edition, Oracle8i Standard Edition, Oracle8i Personal Edition, and Oracle8i Lite.
Updateable snapshots can now be subsetted horizontally (selected rows) or vertically (selected columns). Previous release allow 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 to online instantiation is that the data will be current at instantiation time. However, this is at the cost of requiring a live connection, possibly of long duration.
Offline instantiation allows the DBA to package the deployment templates and required data onto some type of storage media (tape, CD-ROM, and so on) 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 are 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 snapshots. 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. A major 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 Windows platforms. There is also a replication class of events in OEM which, for example, can be used to monitor errors or delinquent snapshot refreshes.
Replication Manager has the following new wizards in Oracle8i:
The integration between the Oracle8i server and Oracle8i Lite has been improved to provide better performance and increased functionality. All of the replication changes previously described are supported, and Oracle8i Lite users with laptops at remote sites will especially benefit from reduced connection time.
Java RepAPI is a runtime library that enables clients to replicate data with Oracle servers. Java RepAPI provides replication services to thin client databases, such as Oracle8i Lite and those running front-office automation applications. With the new deployment template feature in Oracle8i as its foundation, Java RepAPI provides support for LOBs and vertical subsetting of updateable snapshots, using the CORBA Internet Inter-ORB Protocol (IIOP) for communication. Oracle8i supports instantiation of Oracle8i Lite sites while disconnected from the server. Java RepAPI is available only with Oracle release 8.1.6 and higher.
Appendix C, "Configuring the Oracle8i Server for RepAPI" for more information.
The Oracle8 (release 8.0) replication 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. Manageability and security were also enhanced for Oracle8. All of the features described in the following sections also apply to Oracle8i.
Oracle8 provides significant performance improvements based on the following new features.
Oracle8 dramatically improves throughput performance by parallelizing the propagation of a replication transaction stream while maintaining consistency and transaction dependencies.
Oracle8 internalized replication triggers that were external in past releases are now internalized. Internal triggers:
Oracle8 reduces the amount of replicated data propagated over the network. Propagation can be reduced to only the following:
This feature is especially important for performance when replicating LOBs.
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 sales force automation and branch automation.
Oracle8 supports the replication of the following types of large objects:
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 process updates while other master groups are quiesced.
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.
Oracle8 automatically registers information about a snapshot at its associated master site. This facilitates monitoring and distributed administration.
Oracle8 provides utilities to enable you to reorganize master tables while preserving the consistency of master snapshot logs.
Oracle8i Replication Management API Reference for information about reorganizing master tables.
Offline instantiation of schemas and database using Export/Import is now more automatic.
The "Performing an Offline Instantiation Using Export/Import" section in Chapter 7 of Oracle8i Replication Management API Reference.
Updateable snapshots now support declarative referential and uniqueness constraints.
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.
The Oracle8 system-based security model:
Replication Manager now includes several wizards to help you configure your system quickly.
Oracle Replication Manager includes support for most new features of Oracle8 replication, including: