17.2.3 Copying Deferred Transactions to New Destinations
17.2.4 Maintenance Procedures
17.2.5 Propagating Deferred RPCs
17.2.6 Scheduling Propagation (Oracle8 only)
17.3 DBMS_DEFER: Building Deferred Calls
17.3.1 Getting Started with DBMS_DEFER
17.3.2 Basic RPCs
17.3.3 Parameterized RPCs
17.4 DBMS_DEFER_QUERY: Performing Diagnostics and Maintenance
17.4.1 Getting Started with DBMS_DEFER_QUERY
Table of Contents
Part I: Overview
Part II: Application Development Packages
Part III: Server Management Packages
Part IV: Distributed Database Packages
Structure of This Book
Nội dung
heap_size (Oracle8 only) Used only if parallelism > 0. Sets the maximum number of transactions to be examined simultaneously for determining parallel scheduling. Oracle determines this value internally; you are advised not to use it. The MAKE procedure does not raise any exceptions. 14.2.2.1.1 Examples The following examples illustrate how the MAKE procedure may be used. 14.2.2.1.2 Read−only snapshot. group In this example, we create a snapshot refresh group of read−only snapshots: DECLARE vSnapshotList dbms_utility.uncl_array BEGIN vSnapshotList(1) = 'COUNTRIES' vSnapshotList(2) = 'STATES' vSnapshotList(3) = 'POSTAL_CODES' vSnapshotList(4) = 'CUSTOMER_ADDRESSES' DBMS_REFRESH.MAKE(name => 'SG_ADDR_TABS', tab => vSnapShotList, next_date => TRUNC(sysdate) + 1, interval => 'SYSDATE + 1'); END; This example shows the simplest invocation of DBMS_REFRESH.MAKE; defaults are used for all possible parameters. This call creates a snapshot group on four related tables, and schedules them to be refreshed at every day at midnight. 14.2.2.1.3 Read−only snapshot group with specialized parameters In the following example, we create a snapshot refresh group of read−only snapshots with specialized parameters: DECLARE vSnapshotList dbms_utility.uncl_array BEGIN vSnapshotList(1) = 'COUNTRIES' vSnapshotList(2) = 'STATES' vSnapshotList(3) = 'POSTAL_CODES' vSnapshotList(4) = 'CUSTOMER_ADDRESSES' DBMS_REFRESH.MAKE(name => 'SG_ADDR_TABS', tab => vSnapShotList, next_date => TRUNC(sysdate) + 1, interval => 'SYSDATE + 1', implicit_destroy => TRUE, lax => TRUE, rollback_segment 'RB1'); END; This example creates the same snapshot group as in the previous example, but with some additional properties: implicit_destroy = TRUE This setting causes the snapshot group SG_ADDR_TABS to be destroyed if all of the snapshots in the group are dropped. The default behavior is to preserve the snapshot group, even if it has no members. [Appendix A] What's on the Companion Disk? 14.2.2 Creating and Destroying Snapshot Groups 621 lax = TRUE If any of the snapshots being added to SG_ADDR_TABS exist in another snapshot group, this setting instructs Oracle to remove them from the other group before adding them to the new group. A snapshot cannot be a member of more than one snapshot group. rollback_segment = `RB1' This setting causes Oracle to use rollback segment RB1 whenever it refreshes snapshot group SG_ADDR_TABS. You should consider specifying rollback segments if your snapshot refreshes result in long transactions requiring a large rollback segment. 14.2.2.1.4 Parallel propagation In the next example, we create a snapshot refresh group that uses parallel propagation (Oracle8 only): DECLARE vSnapshotList dbms_utility.uncl_array BEGIN vSnapshotList(1) = 'COUNTRIES' vSnapshotList(2) = 'STATES' vSnapshotList(3) = 'POSTAL_CODES' vSnapshotList(4) = 'CUSTOMER_ADDRESSES' DBMS_REFRESH.MAKE(name => 'SG_ADDR_TABS', tab => vSnapShotList, next_date => TRUNC(sysdate) + 1, interval => 'SYSDATE + 1', parallelism => 4,); END; This example sets parallelism to 4, so that Oracle uses four processes to perform the refresh. 14.2.2.2 The DBMS_REFRESH.DESTROY procedure Call the DESTROY procedure to destroy a snapshot group. For both Oracle7 and Oracle8, you call DESTROY as follows, PROCEDURE DBMS_REFRESH.DESTROY (name IN VARCHAR2); where name is the name of the snapshot group to be destroyed. The DESTROY procedure raises the following exception: Name Number Description ORA−23404 −23404 Refresh group name does not exist 14.2.2.2.1 Example This example destroys the snapshot group SG_ADDR_TABS: BEGIN DBMS_REFRESH.DESTROY( name => 'SG_ADDR_TABS' ); END; This example does not drop the member snapshots themselves; however, they will not be refreshed again unless you either add them to another snapshot group, or refresh them manually with the DBMS_SNAPSHOT.REFRESH procedure. [Appendix A] What's on the Companion Disk? 14.2.2 Creating and Destroying Snapshot Groups 622 14.2.3 Adding and Subtracting Snapshots from Snapshot Groups With the ADD and SUBTRACT procedures, you can add and subtract the snapshots in a snapshot group after you have created the group. As with the other DBMS_REFRESH procedures, you must call these procedures from the snapshot site. NOTE: A snapshot group cannot have more than 100 members. 14.2.3.1 The DBMS_REFRESH.ADD procedure Call the ADD procedure to add a snapshot group. The specification follows: PROCEDURE DBMS_REFRESH.ADD (name IN VARCHAR2, {list IN VARCHAR2,| tab IN dbms_utility.uncl_array,} lax IN BOOLEAN DEFAULT FALSE ); The parameters for the ADD procedure have the same meaning as in the MAKE procedure; refer to the parameter table in that section. Note that you must select the list or tab parameter, but not both. The ADD procedure does not raise any exceptions. 14.2.3.1.1 Example This example uses the ADD procedure to add the snapshots PROVINCES and CONTINENTS to the existing snapshot group SG_ARR_TABS: BEGIN DBMS_REFRESH.ADD (name => 'SG_ADDR_TABS', list => 'PROVINCES', CONTINENTS'); END; 14.2.3.2 The DBMS_REFRESH.SUBTRACT procedure Call the SUBTRACT procedure to subtract a snapshot group. The specification follows: PROCEDURE DBMS_REFRESH.SUBTRACT (name IN VARCHAR2, {list IN VARCHAR2,| tab IN dbms_utility.uncl_array,} lax IN BOOLEAN DEFAULT FALSE ); The parameters for the SUBTRACT procedure have the same meaning as in the MAKE procedure; refer to the parameter table in that section. Note that you must select the list or tab parameter, but not both. The SUBTRACT procedure does not raise any exceptions. 14.2.3.2.1 Example The following example removes the snapshots STATES and COUNTRIES from the existing snapshot group SG_ADDR_TABS. Since we also specified lax = TRUE, the call also drops the snapshot group if there are no other member snapshots remaining. BEGIN DBMS_REFRESH.SUBTRACT( name => 'SG_ADDR_TABS', list => 'STATES', COUNTRIES', lax => TRUE); END; [Appendix A] What's on the Companion Disk? 14.2.3 Adding and Subtracting Snapshots from Snapshot Groups 623 14.2.4 Altering Properties of a Snapshot Group The CHANGE procedure allows you to modify settings associated with a snapshot group. You can change any of the parameters that are available in DBMS_REFRESH.MAKE: interval implicit_destroy rollback_segment push_deferred_rpc refresh_after_errors purge_option (Oracle8 only) parallelism (Oracle8 only) heap_size (Oracle8 only) Refer to the MAKE section for an explanation of these parameters. 14.2.4.1 The DBMS_REFRESH.CHANGE procedure Call the CHANGE procedure to modify a snapshot group's setting. The specifications for CHANGE differ for Oracle7 and Oracle8 as follows. Here is the Oracle7 specification: PROCEDURE DBMS_REFRESH.CHANGE (name IN VARCHAR2, next_date IN DATE DEFAULT NULL, interval IN VARCHAR2 DEFAULT NULL, implicit_destroy IN BOOLEAN DEFAULT NULL, rollback_seg IN VARCHAR2 DEFAULT NULL, push_deferred_rpc IN BOOLEAN DEFAULT NULL, refresh_after_errors IN BOOLEAN DEFAULT NULL); Here is the Oracle8 specification: PROCEDURE DBMS_REFRESH.CHANGE (name IN VARCHAR2, next_date IN DATE := NULL, interval IN VARCHAR2 := NULL, implicit_destroy IN BOOLEAN := NULL, rollback_seg IN VARCHAR2 := NULL, push_deferred_rpc IN BOOLEAN := NULL, refresh_after_errors IN BOOLEAN := NULL, purge_option IN BINARY_INTEGER := NULL, parallelism IN BINARY_INTEGER := NULL, heap_size IN BINARY_INTEGER := NULL); As with the MAKE procedure, the difference between the Oracle7 and Oracle8 CHANGE specifications is the inclusion of support for parallel propagation and purging in the Oracle8 version. The CHANGE procedure does not raise any exceptions 14.2.5 Manually Refreshing Snapshot Groups The REFRESH procedure refreshes a snapshot group. [Appendix A] What's on the Companion Disk? 14.2.4 Altering Properties of a Snapshot Group 624 14.2.5.1 The DBMS_REFRESH.REFRESH procedure Call REFRESH to refresh a snapshot group. A call to REFRESH causes all members of snapshot group name to be refreshed with the settings that you have designated in DBMS_REFRESH.MAKE and/or DBMS_REFRESH.CHANGE. The specification is, PROCEDURE DBMS_REFRESH.REFRESH (name IN VARCHAR2); where name identifies the snapshot group. The REFRESH procedure does not raise any exceptions. 14.1 DBMS_SNAPSHOT: Managing Snapshots 14.3 DBMS_OFFLINE_SNAPSHOT: Performing Offline Snapshot Instantiation Copyright (c) 2000 O'Reilly & Associates. All rights reserved. [Appendix A] What's on the Companion Disk? 14.2.5 Manually Refreshing Snapshot Groups 625 . 4, so that Oracle uses four processes to perform the refresh. 14.2.2.2 The DBMS_REFRESH.DESTROY procedure Call the DESTROY procedure to destroy a snapshot group. For both Oracle7 and Oracle8 , you. DBMS_REFRESH.MAKE: interval implicit_destroy rollback_segment push_deferred_rpc refresh_after_errors purge_option (Oracle8 only) parallelism (Oracle8 only) heap_size (Oracle8 only) Refer to the MAKE section for an explanation of these parameters. 14.2.4.1. a snapshot group's setting. The specifications for CHANGE differ for Oracle7 and Oracle8 as follows. Here is the Oracle7 specification: PROCEDURE DBMS_REFRESH.CHANGE (name IN VARCHAR2,