What's New in Advanced Replication?

This section describes the new replication features of Oracle9i release 9.0. New features information from previous releases is also retained to help those users migrating or upgrading to the current release.

The following sections describe the new features in replication:

Oracle9i New Features in Replication

The Oracle9i release 9.0 replication features and enhancements are described in the following sections. Oracle9i extends availability by reducing the need to quiesce the replication environment. Replication sites can remain open to users while certain database administration operations are taking place. Oracle9i also enables you to replicate user-defined types and create materialized views that are based on other materialized views. In addition, you can fast refresh more types of materialized views in Oracle9i.

Extended Availability

Advanced Replication extends the availability of your replication databases by reducing the number of operations that require quiesce of a master group. The tables in your master group can continue to process transactions while these administration operations are taking place.

Quiescing means stopping all replication activity for a master group. When a master group is quiesced, users cannot perform data manipulation language (DML) statements on any of the tables in the master group. Also, all deferred transactions must be propagated before you can quiesce a master group.

The following sections describe operations that no longer require quiesce in release 9.0. In these sections, the replication management API procedures that correspond to each operation are listed.

Note:

Currently, the Replication Management tool in Oracle Enterprise Manager still requires that you quiesce the master group to perform these operations. Use the replication management API procedures listed in the following sections if you do not want to quiesce the master group.

Adding New Master Sites Without Quiescing the Master Group

You can add new master sites to a master group without quiescing the group. Use the following procedures in the DBMS_REPCAT package to complete this operation:
- SPECIFY_NEW_MASTERS
- ADD_NEW_MASTERS
- RESUME_PROPAGATION_TO_MDEF
- PREPARE_INSTANTIATED_MASTER
Altering a Master Table by Making a Safe Change to It in a Single Master Environment

You can use the ALTER_MASTER_REPOBJECT procedure in the DBMS_REPCAT package to make safe changes to a replicated object in a single master environment. Quiesce is still required for these changes in a multimaster environment.

See Also:
Oracle9i Replication Management API Reference for detailed information about using the procedures described previously in this section

Support for User-Defined Types

You can replicate user-defined types and the database objects that are based on them in both a multimaster replication environment and a materialized view replication environment. The database objects that you can replicate include:
- Tables with column objects
- Object tables
- Tables with nested tables, including the storage tables of nested tables
- Tables with varrays
- Tables with REF columns
- Indextypes
- User-defined operators
Oracle9i also supports replication of multilevel collections.
See Also:

"Replication of User-Defined Types"

"Materialized Views with User-Defined Types"

Multitier Materialized Views

The multitier materialized view feature enables you to create a materialized view that is based on another materialized view, instead of on a master table at a master site. These materialized views function in the same way as materialized views that are based on master tables, and they can be read-only or updatable.

See Also:
"Multitier Materialized Views"

Fast Refresh Enhancements for Materialized Views

Performance improvements make refreshing materialized views faster in release 9.0. Also, release 9.0 extends fast refresh capabilities for materialized views by enabling you to fast refresh the following types of materialized views:
- Materialized views with one to many subqueries
- Materialized views with many to many subqueries
- Materialized views with subqueries and unions
Some restrictions apply.

See Also:
"Data Subsetting with Materialized Views"

Performance Monitoring in Replication Environments

The following are new dynamic performance views for performance monitoring:
- V$MVREFRESH contains information about local materialized views that are currently being refreshed. This information is visible only on the materialized view site.
- V$REPLPROP contains information about the parallel propagation currently in progress at the replication site.
- V$REPLQUEUE contains statistics about the deferred transactions queue.
In addition, the DEFSCHEDULE data dictionary view is enhanced for performance monitoring. The following columns are added to the DEFSCHEDULE data dictionary view:
- TOTAL_TXN_COUNT
- AVG_THROUGHPUT
- AVG_LATENCY
- TOTAL_BYTES_SENT
- TOTAL_BYTES_RECEIVED
- TOTAL_ROUND_TRIPS
- TOTAL_ADMIN_COUNT
- TOTAL_ERROR_COUNT
- TOTAL_SLEEP_TIME
  
  See Also:
  Oracle9i Replication Management API Reference for detailed information about these views

Row-Level Dependency Tracking for Parallel Propagation

You can track dependencies between transactions at the row level instead of at the data block level. This feature enables parallel propagation to track dependencies and order changes more efficiently when applying the deferred transaction queue. This increased efficiency improves performance and provides greater scalability in replication environments.

See Also:
"Replication Protection Mechanisms"

Replication Support for CHAR Column Length Semantics and Unicode

Replication supports CHAR column length semantics and Unicode in both multimaster environments and materialized view environments.

See Also:
Appendix B, "Column Length Semantics and Unicode"

Improvements to the Replication Management Tool

Oracle has improved the Replication Management tool in Oracle9i with the following features:
- Reporting capabilities
- Redesigned Deployment Template Wizard and Template Script Generation Wizard (formerly called the Offline Instantiation Wizard)
In addition, the Replication Management tool is integrated with the Oracle Enterprise Manager Console in Oracle9i.

See Also:
Chapter 7, "Replication Management Tool Introduction" and the Replication Management tool online help

Oracle8i New Features in Replication

The Oracle8i (release 8.1) replication features and enhancements described in this section comprise the overall effort to optimize replication performance and make materialized view environment distribution and security more effective. All of the features described in the following sections also apply to Oracle9i.

Extended Availability for Single Master Replication Environments

Release 8.1.7 and higher reduces the number of operations that require you to quiesce a master group in a single master replication environment. The following sections describe operations that no longer require quiesce in single master environments. In these sections, the replication management API procedure that corresponds to each operation is listed.

Note:
The extended availability feature only applies to single master replication environments, not to multimaster environments.

Extended Availability in All Single Master Environments

The following table lists the operations that no longer require quiesce in all single master replication environments. This table also lists the procedure in the DBMS_REPCAT package that corresponds to each operation. In addition, these operations no longer require quiesce when you are using the Replication Management tool in DBA Studio (in release 8.1.7) or the Oracle Enterprise Manager Console (in Oracle9i).

Operation	DBMS_REPCAT Procedure
Designating a method for resolving a delete conflict	`ADD_DELETE_RESOLUTION`
Adding a member to a priority group	`ADD_PRIORITY_``datatype`
Adding a new site to a site priority group	`ADD_SITE_PRIORITY_SITE`
Designating a method for resolving a uniqueness conflict	`ADD_UNIQUE_RESOLUTION`
Designating a method for resolving an update conflict	`ADD_UPDATE_RESOLUTION`
Altering the priority level associated with a specified priority group member	`ALTER_PRIORITY`
Altering the value of a member in a priority group	`ALTER_PRIORITY_``datatype`
Altering the priority level associated with a specified site	`ALTER_SITE_PRIORITY`
Altering the site associated with a specified priority level	`ALTER_SITE_PRIORITY_SITE`
Specifying whether to compare old column values at each master site for each nonkey column of a replicated table when executing updates and deletes	`COMPARE_OLD_VALUES`
Specifying that an object is a replicated object	`CREATE_MASTER_REPOBJECT`
Creating a priority group for conflict resolution	`DEFINE_PRIORITY_GROUP`
Creating a new site priority group for a replicated master group for conflict resolution	`DEFINE_SITE_PRIORITY`
Dropping a delete conflict resolution method	`DROP_DELETE_RESOLUTION`
Dropping a member of a priority group by priority level	`DROP_PRIORITY`
Dropping a member of a priority group by value	`DROP_PRIORITY_``datatype`
Dropping a priority group	`DROP_PRIORITY_GROUP`
Dropping a site priority group	`DROP_SITE_PRIORITY`
Dropping a specified site, by name, from a site priority group	`DROP_SITE_PRIORITY_SITE`
Dropping a uniqueness conflict resolution method	`DROP_UNIQUE_RESOLUTION`
Dropping an update conflict resolution method	`DROP_UPDATE_RESOLUTION`
Generating the triggers, packages, and procedures needed to support replication for a specified object	`GENERATE_REPLICATION_SUPPORT`
Specifying whether to send old column values for each nonkey column of a replicated table when executing updates and deletes	`SEND_OLD_VALUES`

Extended Availability In Single Master Environments Not Using Minimum Communication

In a single master environment, if none of the updatable materialized views use minimum communication in the detection of conflicts, then quiesce is no longer required for the administration operations to the master group listed in the following table. This table also lists the procedure in the DBMS_REPCAT package that corresponds to each operation. In addition, these operations no longer require quiesce when you are using the Replication Management tool in DBA Studio (in release 8.1.7) or the Oracle Enterprise Manager Console (in Oracle9i).

Note:

If at least one updatable materialized view is using minimum communication, then quiesce is not required if you perform the actions described in "Reduced Quiesce and Materialized Views in a Single Master Site Environment"

Operation	DBMS_REPCAT Procedure
Adding members to an existing column group	`ADD_GROUPED_COLUMN`
Creating an empty column group	`DEFINE_COLUMN_GROUP`
Dropping a column group	`DROP_COLUMN_GROUP`
Removing members from a column group	`DROP_GROUPED_COLUMN`
Creating a new column group with one or more members	`MAKE_COLUMN_GROUP`
Specifying use of an alternate column or group of columns, instead of the primary key, to determine which columns of a table to compare when using row-level replication	`SET_COLUMNS`

See Also:

Oracle9i Replication Management API Reference for detailed information about using the procedures described previously in this section

Performance Improvements

Significant performance gains are realized by the internalization of PL/SQL replication packages and by optimizations to materialized view refresh.
- Internal Apply Packages
  
  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.
  
  See Also:
  Chapter 2, "Master Replication Concepts and Architecture"

Faster Materialized View Refresh

Materialized view refresh has been optimized to support large refresh groups. There is improved support for subquery materialized views, and for null refresh (no changes to the master tables since the last refresh). A single refresh group can now contain 400 materialized views, and the number of round-trips required to refresh materialized views in a refresh group has been reduced.

See Also:
Chapter 3, "Materialized View Concepts and Architecture"

Improved Mass Deployment Support

Oracle has improved replication support for the growing market of front office applications, in particular mass deployment.
- Instantiation of Materialized View Sites Using Deployment Templates
  
  Materialized view deployment templates can be instantiated online or offline. Online instantiation allows a materialized view 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 materialized view 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.
  
  See Also:
  "Deployment Template Packaging and Instantiation"

Parameterized Materialized View Deployment Templates

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 materialized views and other database objects to be instantiated at a node. They allow a DBA to centrally package a materialized view 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. A 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 materialized view environments at the following types of materialized view sites: Oracle Enterprise Edition, Oracle Standard Edition, and Oracle Personal Edition.

See Also:
Chapter 4, "Deployment Templates Concepts and Architecture"

Column Subsetting of Updatable Materialized Views

Updatable materialized views can now be subsetted by rows and columns. Previous release allow row subsetting only. Column subsetting allows the deployment of the minimum amount of data needed by a remote site, thus reducing connection time. It also protects materialized view sites from changes to their associated masters. A column can be added to a master site without impacting the materialized view site, or a column can be deleted and not impact the materialized view site, if the materialized view site does not currently reference that column.
See Also:

"Data Subsetting with Materialized Views"

"Column Subsetting with Deployment Templates"

"Row Subsetting"

Improved Security

While the scripts used to instantiate a materialized view site are generated at the master site and can control access to data, it is still necessary to connect to a receiver and proxy materialized view administrator to propagate replicated transactions and to refresh materialized views. Oracle8i enhancements to the replication security model eliminate certain security deficiencies regarding the granting of privileges to untrusted sites.
- Object privileges, as required by a receiver of remote procedure calls (RPCs) at a master site, are now automatically managed. Only required object privileges are granted to untrusted sites.
- Proxy materialized view administrators now have a way of accessing objects in replication groups without being granted excessive privileges.
  
  See Also:
  Oracle9i Replication Management API Reference

The Replication Management Tool

A number of improvements have been made to the Oracle Replication Management tool. A major enhancement is that it has been rewritten to conform to the new Java interface of Oracle Enterprise Manager. The Replication Management tool can now be run from anywhere in the network, and it is not constrained to Windows platforms. The Replication Management tool can also be run using a standard web browser. In addition, Oracle Enterprise Manager includes a replication class of events which, for example, can be used to monitor errors or delinquent materialized view refreshes.

The Replication Management tool has the following new wizards in Oracle8i:
- Deployment Template Wizard for creating deployment templates
- Offline Instantiation Wizard for packaging a deployment template for offline instantiation
  
  See Also:
  Chapter 7, "Replication Management Tool Introduction" and the Replication Management tool online help

Oracle8 New Features in Replication

The Oracle8 (release 8.0) replication features and enhancements described in the following section comprise the overall effort to optimize multimaster replication performance and make certain types of materialized view 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 and Oracle9i.

Performance Enhancements

Oracle8 provides significant performance improvements based on the following new features.
- Parallel Propagation of Deferred Transactions
  
  Oracle8 dramatically improves throughput performance by parallelizing the propagation of a replication transaction stream while maintaining consistency and transaction dependencies.
  
  See Also:
  "Guidelines for Scheduled Links"

Internalized Replication Triggers

Oracle8 internalized replication triggers that were external in past releases are now internalized. Internal triggers:
- Improve response time performance
- Reduce processing overhead
- Require less administration
  
  See Also:
  Chapter 2, "Master Replication Concepts and Architecture"

Reduced Data Propagation

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
- Primary key values
You accomplish this by:
- Using the min_communication parameter in various procedures in the DBMS_REPCAT package and the DBMS_OFFLINE_SNAPSHOT package
- Using the SEND_OLD_VALUES and COMPARE_OLD_VALUES procedures in the DBMS_REPCAT package
This feature is especially important for performance when replicating LOBs.

See Also:
"Minimum Communication"

Data Subsetting Based on Subqueries

Materialized views 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.

See Also:
"Data Subsetting with Materialized Views"

Large Object Datatypes (LOBs) Support

Oracle8 supports the replication of the following types of large objects:
- Binary LOBs (BLOBs)
- Character LOBs (CLOBs)
- Globalization Support for character LOBs (NCLOBs)
  
  Note:
  Globalization Support in Oracle9i was formerly known as National Language Support.
  
  See Also:
  The Replication Management tool online help for information on replicating object definitions to master sites and "Datatype Considerations"

Improved Management and Ease of Use

Oracle8 facilitates database management with the following features.
- Fine Grained Quiesce
  
  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.
  
  See Also:
  "Replication Modes of Operation"

Primary Key Materialized Views

Primary key materialized views allow you to reorganize master tables while preserving fast refresh capability. Oracle8 adds primary key materialized views as the default and continues to support ROWID materialized views.

See Also:
"Available Materialized Views". Also, see Oracle9i Database Migration for information about using ROWID materialized views in Oracle8 and higher.

Materialized View Registration at Master Sites

Oracle8 automatically registers information about a materialized view at its associated master site. This facilitates monitoring and distributed administration.

See Also:
"Materialized View Registration at a Master Site or Master Materialized View Site"

Reorganizing Tables With Capability of Fast Refresh

Oracle8 provides utilities to enable you to reorganize master tables while preserving the consistency of materialized view logs.

See Also:
Oracle9i Replication Management API Reference for information about reorganizing master tables

Support for Offline Instantiation Using Export/Import

Offline instantiation of schemas and database using export/import is now more automatic.

See Also:
Oracle9i Replication Management API Reference for more information about adding new master sites using export/import

Deferred Constraints for Updatable Materialized Views

Updatable materialized views now support declarative referential and uniqueness constraints.
Partitioned Tables and Indexes

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.

Enhanced, System-Based Security Model

The Oracle8 system-based security model:
- Improves consistency because a single system-level model operates the same way in both synchronous and asynchronous environments
- Improves reliability because transactions are less likely to fail due to the lack of privileges at the receiving sites
- Simplifies links because a single user can act as repadmin user and repsys user
- Eliminates the need for a "user-level" model
- Allows one or more materialized view owners to perform materialized view refresh
  
  See Also:
  Oracle9i Replication Management API Reference

New Replication Management Tool Features

The Replication Management tool now includes several wizards to help you configure your system quickly.
- Setup Wizard for set up of multimaster configurations, including account, schema, and link creation
- Setup Wizard for set up of materialized view site configurations, including account, schema, and link creation
- Materialized View Group Wizard for set up of materialized view groups.
The Replication Management tool includes support for most new features of Oracle8 replication, including:
- Automatic recognition of each site's database version and dynamic configuration to manage release 9.x, release 8.x, and release 7.3 databases
- Support for managing materialized view logs
- Easy entry of date and interval expressions for jobs, refresh groups, and scheduled links
- For Oracle8 databases, a flag to indicate that a table requires regeneration of replication support
- Support for registering a site's replication administrator and propagator
- A database objects folder to display database objects for master groups
- Support for the validation of a master group at all master sites
  
  See Also:
  Chapter 7, "Replication Management Tool Introduction" and the Replication Management tool online help