12
Simple Single Source Replication Example

This chapter illustrates an example of a simple single source replication environment that can be constructed using Streams.

This chapter contains these topics:

• Overview of the Simple Single Source Replication Example
• Prerequisites
• Set Up Users and Create Queues and Database Links
• Configure Capture, Propagation, and Apply for Changes to One Table
• Make Changes to the hr.jobs Table and View Results

Overview of the Simple Single Source Replication Example

The example in this chapter illustrates using Streams to replicate data in one table between two databases. A capture process captures data manipulation language (DML) and data definition language (DDL) changes made to the jobs table in the hr schema at the str1.net Oracle database, and a propagation propagates these changes to the str2.net Oracle database. Next, an apply process applies these changes at the str2.net database. This example assumes that the hr.jobs table is read-only at the str2.net database.

Figure 12-1 provides an overview of the environment.

Figure 12-1 Simple Example That Shares Data From a Single Source Database

Text description of the illustration strep035.gif

Prerequisites

The following prerequisites must be completed before you begin the example in this chapter.

• Set the following initialization parameters to the values indicated:
  • GLOBAL_NAMES: This parameter must be set to true at each database that is participating in your Streams environment.
  • JOB_QUEUE_PROCESSES: This parameter must be set to at least 2 at each database that is propagating events in your Streams environment. It should be set to the same value as the maximum number of jobs that can run simultaneously plus one. In this example, str1.net propagates events. So, JOB_QUEUE_PROCESSES must be set to at least 2 at str1.net.
  • COMPATIBLE: This parameter must be set to 10.1.0 or higher at each database that is participating in your Streams environment.
  • STREAMS_POOL_SIZE: Optionally set this parameter to an appropriate value for each database in the environment. This parameter specifies the size of the Streams pool. The Streams pool contains captured events. In addition, the Streams pool is used for internal communications during parallel capture and apply. If STREAMS_POOL_SIZE is set to zero (the default), then Streams uses the shared pool. In this case, you may need to increase the size of the shared pool at each database.

    See Also: Oracle Streams Concepts and Administration for information about other initialization parameters that are important in a Streams environment

• Any database producing changes that will be captured must be running in ARCHIVELOG mode. In this example, changes are produced at str1.net, and so str1.net must be running in ARCHIVELOG mode.

  See Also: Oracle Database Administrator's Guide for information about running a database in ARCHIVELOG mode

• Configure your network and Oracle Net so that the str1.net database can communicate with the str2.net database.

  See Also: Oracle Net Services Administrator's Guide

• This example creates a new user to function as the Streams administrator (strmadmin) at each database and prompts you for the tablespace you want to use for this user's data. Before you start this example, either create a new tablespace or identify an existing tablespace for the Streams administrator to use at each database. The Streams administrator should not use the SYSTEM tablespace.

Set Up Users and Create Queues and Database Links

Complete the following steps to set up users and create queues and database links for a Streams replication environment that includes two Oracle databases.

1. Show Output and Spool Results
2. Set Up Users at str1.net
3. Create the SYS.AnyData Queue at str1.net
4. Create the Database Link at str1.net
5. Set Up Users at str2.net
6. Set Up the SYS.AnyData Queue at str2.net
7. Check the Spool Results

/************************* BEGINNING OF SCRIPT ******************************

Step 1 Show Output and Spool Results

Run SET ECHO ON and specify the spool file for the script. Check the spool file for errors after you run this script.

*/

SET ECHO ON
SPOOL streams_setup_simple.out

/*

Step 2 Set Up Users at str1.net

Connect to str1.net as SYS user.

*/
 
CONNECT SYS/CHANGE_ON_INSTALL@str1.net AS SYSDBA

/*

Create the Streams administrator named strmadmin and grant this user the necessary privileges. These privileges enable the user to manage queues, execute subprograms in packages related to Streams, create rule sets, create rules, and monitor the Streams environment by querying data dictionary views and queue tables. You may choose a different name for this user.

*/

GRANT CONNECT, RESOURCE, DBA, SELECT_CATALOG_ROLE 
  TO strmadmin IDENTIFIED BY strmadminpw;

ACCEPT streams_tbs PROMPT 'Enter Streams administrator tablespace on str1.net: '

ALTER USER strmadmin DEFAULT TABLESPACE &streams_tbs
                     QUOTA UNLIMITED ON &streams_tbs;

/*

Step 3 Create the SYS.AnyData Queue at str1.net

Connect as the Streams administrator at the database where you want to capture changes. In this example, that database is str1.net.

*/

CONNECT strmadmin/strmadminpw@str1.net

/*

Run the SET_UP_QUEUE procedure to create a queue named streams_queue at str1.net. This queue will function as the SYS.AnyData queue by holding the captured changes that will be propagated to other databases.

Running the SET_UP_QUEUE procedure performs the following actions:

• Creates a queue table named streams_queue_table. This queue table is owned by the Streams administrator (strmadmin) and uses the default storage of this user.
• Creates a queue named streams_queue owned by the Streams administrator (strmadmin).
• Starts the queue.

*/

EXEC DBMS_STREAMS_ADM.SET_UP_QUEUE();

/*

Step 4 Create the Database Link at str1.net

Create the database link from the database where changes are captured to the database where changes are propagated. In this example, the database where changes are captured is str1.net, and these changes are propagated to str2.net.

*/

CREATE DATABASE LINK str2.net CONNECT TO strmadmin IDENTIFIED BY strmadminpw 
   USING 'str2.net';

/*

Step 5 Set Up Users at str2.net

Connect to str2.net as SYS user.

*/
 
CONNECT SYS/CHANGE_ON_INSTALL@str2.net AS SYSDBA

/*

Create the Streams administrator named strmadmin and grant this user the necessary privileges. These privileges enable the user to manage queues, execute subprograms in packages related to Streams, create rule sets, create rules, and monitor the Streams environment by querying data dictionary views and queue tables. In this example, the Streams administrator will be the apply user for the apply process and must be able to apply changes to the hr.jobs table at str2.net. Therefore, the Streams administrator is granted ALL privileges on this table. You may choose a different name for the Streams administrator.

*/
 
GRANT CONNECT, RESOURCE, DBA, SELECT_CATALOG_ROLE 
  TO strmadmin IDENTIFIED BY strmadminpw;

ACCEPT streams_tbs PROMPT 'Enter Streams administrator tablespace on str2.net: '

ALTER USER strmadmin DEFAULT TABLESPACE &streams_tbs
                     QUOTA UNLIMITED ON &streams_tbs;

GRANT ALL ON hr.jobs TO strmadmin;

/*

Step 6 Set Up the SYS.AnyData Queue at str2.net

Connect as the Streams administrator at str2.net.

*/

CONNECT strmadmin/strmadminpw@str2.net

/*

Run the SET_UP_QUEUE procedure to create a queue named streams_queue at str2.net. This queue will function as the SYS.AnyData queue by holding the changes that will be applied at this database.

Running the SET_UP_QUEUE procedure performs the following actions:

• Creates a queue table named streams_queue_table. This queue table is owned by the Streams administrator (strmadmin) and uses the default storage of this user.
• Creates a queue named streams_queue owned by the Streams administrator (strmadmin).
• Starts the queue.

*/

EXEC  DBMS_STREAMS_ADM.SET_UP_QUEUE();

/*

Step 7 Check the Spool Results

Check the streams_setup_simple.out spool file to ensure that all actions finished successfully after this script is completed.

*/

SET ECHO OFF
SPOOL OFF

/*************************** END OF SCRIPT ******************************/

Configure Capture, Propagation, and Apply for Changes to One Table

Complete the following steps to specify the capture, propagation, and apply definitions for the hr.jobs table using the DBMS_STEAMS_ADM package.

1. Show Output and Spool Results
2. Specify Supplemental Logging at str1.net
3. Configure Propagation at str1.net
4. Configure the Capture Process at str1.net
5. Set the Instantiation SCN for the hr.jobs Table at str2.net
6. Configure the Apply Process at str2.net
7. Start the Apply Process at str2.net
8. Start the Capture Process at str1.net
9. Check the Spool Results

/************************* BEGINNING OF SCRIPT ******************************

Step 1 Show Output and Spool Results

Run SET ECHO ON and specify the spool file for the script. Check the spool file for errors after you run this script.

*/

SET ECHO ON
SPOOL streams_share_jobs.out

/*

Step 2 Specify Supplemental Logging at str1.net

Connect to str1.net as SYS user.

*/
 
CONNECT SYS/CHANGE_ON_INSTALL@str1.net AS SYSDBA

/*

Supplemental logging places additional information in the redo log for changes made to tables. The apply process needs this extra information to perform certain operations, such as unique row identification and conflict resolution. Because str1.net is the only database where changes are captured in this environment, it is the only database where you must specify supplemental logging for the hr.jobs table.

The following statement specifies an unconditional supplemental log group for the primary key column in the hr.jobs table.

*/

ALTER TABLE hr.jobs ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY) COLUMNS;

/*

Step 3 Configure Propagation at str1.net

Connect to str1.net as the strmadmin user.

*/
 
CONNECT strmadmin/strmadminpw@str1.net

/*

Configure and schedule propagation of DML and DDL changes to the hr.jobs table from the queue at str1.net to the queue at str2.net.

*/

BEGIN
  DBMS_STREAMS_ADM.ADD_TABLE_PROPAGATION_RULES(
    table_name              => 'hr.jobs', 
    streams_name            => 'str1_to_str2', 
    source_queue_name       => 'strmadmin.streams_queue',
    destination_queue_name  => 'strmadmin.streams_queue@str2.net',
    include_dml             => true,
    include_ddl             => true,
    source_database         => 'str1.net',
    inclusion_rule          => true);
END;
/

/*

Step 4 Configure the Capture Process at str1.net

Configure the capture process to capture changes to the hr.jobs table at str1.net. This step specifies that changes to this table are captured by the capture process and enqueued into the specified queue.

*/

BEGIN
  DBMS_STREAMS_ADM.ADD_TABLE_RULES(
    table_name     => 'hr.jobs',   
    streams_type   => 'capture',
    streams_name   => 'capture_simp',
    queue_name     => 'strmadmin.streams_queue',
    include_dml    => true,
    include_ddl    => true,
    inclusion_rule => true);
END;
/

/*

Step 5 Set the Instantiation SCN for the hr.jobs Table at str2.net

This example assumes that the hr.jobs table exists at both the str1.net database and the str2.net database, and that this table is synchronized at these databases. Because the hr.jobs table already exists at str2.net, this example uses the GET_SYSTEM_CHANGE_NUMBER function in the DBMS_FLASHBACK package at str1.net to obtain the current SCN for the source database. This SCN is used at str2.net to run the SET_TABLE_INSTANTIATION_SCN procedure in the DBMS_APPLY_ADM package. Running this procedure sets the instantiation SCN for the hr.jobs table at str2.net.

The SET_TABLE_INSTANTIATION_SCN procedure controls which LCRs for a table are ignored by an apply process and which LCRs for a table are applied by an apply process. If the commit SCN of an LCR for a table from a source database is less than or equal to the instantiation SCN for that table at a destination database, then the apply process at the destination database discards the LCR. Otherwise, the apply process applies the LCR.

In this example, both of the apply process at str2.net will apply transactions to the hr.jobs table with SCNs that were committed after SCN obtained in this step.

*/

DECLARE
  iscn  NUMBER;         -- Variable to hold instantiation SCN value
BEGIN
  iscn := DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER();
  DBMS_APPLY_ADM.SET_TABLE_INSTANTIATION_SCN@STR2.NET(
    source_object_name    => 'hr.jobs',
    source_database_name  => 'str1.net',
    instantiation_scn     => iscn);
END;
/

/*

Step 6 Configure the Apply Process at str2.net

Connect to str2.net as the strmadmin user.

*/
 
CONNECT strmadmin/strmadminpw@str2.net

/*

Configure str2.net to apply changes to the hr.jobs table.

*/

BEGIN
  DBMS_STREAMS_ADM.ADD_TABLE_RULES(
    table_name      => 'hr.jobs',
    streams_type    => 'apply', 
    streams_name    => 'apply_simp',
    queue_name      => 'strmadmin.streams_queue',
    include_dml     => true,
    include_ddl     => true,
    source_database => 'str1.net',
    inclusion_rule  => true);
END;
/

/*

Step 7 Start the Apply Process at str2.net

Set the disable_on_error parameter to n so that the apply process will not be disabled if it encounters an error, and start the apply process at str2.net.

*/

BEGIN
  DBMS_APPLY_ADM.SET_PARAMETER(
    apply_name  => 'apply_simp', 
    parameter   => 'disable_on_error', 
    value       => 'n');
END;
/
 
BEGIN
  DBMS_APPLY_ADM.START_APPLY(
    apply_name  => 'apply_simp');
END;
/

/*

Step 8 Start the Capture Process at str1.net

Connect to str1.net as the strmadmin user.

*/
 
CONNECT strmadmin/strmadminpw@str1.net

/*

Start the capture process at str1.net.

*/

BEGIN
  DBMS_CAPTURE_ADM.START_CAPTURE(
    capture_name  => 'capture_simp');
END;
/

/*

Step 9 Check the Spool Results

Check the streams_share_jobs.out spool file to ensure that all actions finished successfully after this script is completed.

*/

SET ECHO OFF
SPOOL OFF

/*************************** END OF SCRIPT ******************************/

Make Changes to the hr.jobs Table and View Results

Complete the following steps to make DML and DDL changes to the hr.jobs table at str1.net and then confirm that the changes were captured at str1.net, propagated from str1.net to str2.net, and applied to the hr.jobs table at str2.net.

Step 1 Make Changes to hr.jobs at str1.net

Make the following changes to the hr.jobs table.

CONNECT hr/hr@str1.net

UPDATE hr.jobs SET max_salary=9545 WHERE job_id='PR_REP';
COMMIT;

ALTER TABLE hr.jobs ADD(duties VARCHAR2(4000));

Step 2 Query and Describe the hr.jobs Table at str2.net

After some time passes to allow for capture, propagation, and apply of the changes performed in the previous step, run the following query to confirm that the UPDATE change was propagated and applied at str2.net:

CONNECT hr/hr@str2.net

SELECT * FROM hr.jobs WHERE job_id='PR_REP';

The value in the max_salary column should be 9545.

Next, describe the hr.jobs table to confirm that the ALTER TABLE change was propagated and applied at str2.net:

DESC hr.jobs

The duties column should be the last column.