16 Managing Staging and Propagation

Enabling a User to Perform Operations on a Secure Queue

For a user to perform queue operations, such as enqueue and dequeue, on a secure queue, the user must be configured as a secure queue user of the queue. If you use the SET_UP_QUEUE procedure in the DBMS_STREAMS_ADM package to create the secure queue, then the queue owner and the user specified by the queue_user parameter are configured as secure users of the queue automatically. If you want to enable other users to perform operations on the queue, then you can configure these users in one of the following ways:

• Run SET_UP_QUEUE and specify a queue_user. Queue creation is skipped if the queue already exists, but a new queue user is configured if one is specified.

• Associate the user with an Oracle Streams Advanced Queuing (AQ) agent manually.

The following example illustrates associating a user with an Oracle Streams AQ agent manually. Suppose you want to enable the oe user to perform queue operations on a queue named streams_queue. The following steps configure the oe user as a secure queue user of streams_queue:

1. In SQL*Plus, connect as an administrative user who can create Oracle Streams AQ agents and alter users.

   See Oracle Database Administrator's Guide for information about connecting to a database in SQL*Plus.

2. Create an agent:

   EXEC DBMS_AQADM.CREATE_AQ_AGENT(agent_name => 'streams_queue_agent');
   

3. If the user must be able to dequeue messages from queue, then make the agent a subscriber of the secure queue:

   DECLARE
     subscriber SYS.AQ$_AGENT;
   BEGIN
     subscriber :=  SYS.AQ$_AGENT('streams_queue_agent', NULL, NULL);  
     DBMS_AQADM.ADD_SUBSCRIBER(
       queue_name          =>  'strmadmin.streams_queue',
       subscriber          =>  subscriber,
       rule                =>  NULL,
       transformation      =>  NULL);
   END;
   /
   

4. Associate the user with the agent:

   BEGIN
     DBMS_AQADM.ENABLE_DB_ACCESS(
       agent_name  => 'streams_queue_agent',
       db_username => 'oe');
   END;
   /
   

5. Grant the user EXECUTE privilege on the DBMS_STREAMS_MESSAGING package or the DBMS_AQ package, if the user is not already granted these privileges:

   GRANT EXECUTE ON DBMS_STREAMS_MESSAGING TO oe;
   
   GRANT EXECUTE ON DBMS_AQ TO oe;
   

When these steps are complete, the oe user is a secure user of the streams_queue queue and can perform operations on the queue. You still must grant the user specific privileges to perform queue operations, such as enqueue and dequeue privileges.

Disabling a User from Performing Operations on a Secure Queue

You might want to disable a user from performing queue operations on a secure queue for the following reasons:

• You dropped a capture process or a synchronous capture, but you did not drop the queue that was used by the capture process or synchronous capture, and you do not want the user who was the capture user to be able to perform operations on the remaining secure queue.

• You dropped an apply process, but you did not drop the queue that was used by the apply process, and you do not want the user who was the apply user to be able to perform operations on the remaining secure queue.

• You used the ALTER_APPLY procedure in the DBMS_APPLY_ADM package to change the apply_user for an apply process, and you do not want the old apply_user to be able to perform operations on the apply process's queue.

• You enabled a user to perform operations on a secure queue by completing the steps described in Enabling a User to Perform Operations on a Secure Queue, but you no longer want this user to be able to perform operations on the secure queue.

To disable a secure queue user, you can revoke ENQUEUE and DEQUEUE privilege on the queue from the user, or you can run the DISABLE_DB_ACCESS procedure in the DBMS_AQADM package. For example, suppose you want to disable the oe user from performing queue operations on a queue named streams_queue.

1. Run the following procedure to disable the oe user from performing queue operations on the secure queue streams_queue:

   BEGIN
     DBMS_AQADM.DISABLE_DB_ACCESS(
       agent_name  => 'streams_queue_agent',
       db_username => 'oe');
   END;
   /
   

2. If the agent is no longer needed, you can drop the agent:

   BEGIN
     DBMS_AQADM.DROP_AQ_AGENT(
       agent_name  => 'streams_queue_agent');
   END;
   /
   

3. Revoke privileges on the queue from the user, if the user no longer needs these privileges.

   BEGIN
     DBMS_AQADM.REVOKE_QUEUE_PRIVILEGE (
      privilege   => 'ALL',
      queue_name  => 'strmadmin.streams_queue',
      grantee     => 'oe');
   END;
   /
   

Removing a Queue

You use the REMOVE_QUEUE procedure in the DBMS_STREAMS_ADM package to remove an existing ANYDATA queue. When you run the REMOVE_QUEUE procedure, it waits until any existing messages in the queue are consumed. Next, it stops the queue, which means that no further enqueues into the queue or dequeues from the queue are allowed. When the queue is stopped, it drops the queue.

You can also drop the queue table for the queue if it is empty and is not used by another queue. To do so, specify TRUE, the default, for the drop_unused_queue_table parameter.

In addition, you can drop any Oracle Streams clients that use the queue by setting the cascade parameter to TRUE. By default, the cascade parameter is set to FALSE.

For example, to remove an ANYDATA queue named streams_queue in the strmadmin schema and drop its empty queue table, run the following procedure:

BEGIN
  DBMS_STREAMS_ADM.REMOVE_QUEUE(
    queue_name              => 'strmadmin.streams_queue',
    cascade                 => FALSE,
    drop_unused_queue_table => TRUE);
END;
/

In this case, because the cascade parameter is set to FALSE, this procedure drops the streams_queue only if no Oracle Streams clients use the queue. If the cascade parameter is set to FALSE and any Oracle Streams client uses the queue, then an error is raised.

Starting a Propagation

You run the START_PROPAGATION procedure in the DBMS_PROPAGATION_ADM package to start an existing propagation. For example, the following procedure starts a propagation named strm01_propagation:

BEGIN
  DBMS_PROPAGATION_ADM.START_PROPAGATION(
    propagation_name => 'strm01_propagation');
END;
/

Stopping a Propagation

You run the STOP_PROPAGATION procedure in the DBMS_PROPAGATION_ADM package to stop an existing propagation. For example, the following procedure stops a propagation named strm01_propagation:

BEGIN
  DBMS_PROPAGATION_ADM.STOP_PROPAGATION(
    propagation_name => 'strm01_propagation',
    force            => FALSE);
END;
/

To clear the statistics for the propagation when it is stopped, set the force parameter to TRUE. If there is a problem with a propagation, then stopping the propagation with the force parameter set to TRUE and restarting the propagation might correct the problem. If the force parameter is set to FALSE, then the statistics for the propagation are not cleared.

Altering the Schedule of a Propagation Job

To alter the schedule of an existing propagation job, use the ALTER_PROPAGATION_SCHEDULE procedure in the DBMS_AQADM package. The following sections contain examples that alter the schedule of a propagation job for a queue-to-queue propagation and for a queue-to-dblink propagation. These examples set the propagation job to propagate messages every 15 minutes (900 seconds), with each propagation lasting 300 seconds, and a 25-second wait before new messages in a completely propagated queue are propagated.

This section contains these topics:

• Altering the Schedule of a Propagation Job for a Queue-to-Queue Propagation

• Altering the Schedule of a Propagation Job for a Queue-to-Dblink Propagation

BEGIN
  DBMS_AQADM.ALTER_PROPAGATION_SCHEDULE(
   queue_name        => 'strmadmin.strm_a_queue',
   destination       => 'dbs2.example.com',
   duration          => 300,
   next_time         => 'SYSDATE + 900/86400',
   latency           => 25,
   destination_queue => 'strmadmin.strm_b_queue'); 
END;
/

BEGIN
  DBMS_AQADM.ALTER_PROPAGATION_SCHEDULE(
   queue_name  => 'strmadmin.streams_queue',
   destination => 'dbs3.example.com',
   duration    => 300,
   next_time   => 'SYSDATE + 900/86400',
   latency     => 25); 
END;
/

Specifying the Rule Set for a Propagation

You can specify one positive rule set and one negative rule set for a propagation. The propagation propagates a message if it evaluates to TRUE for at least one rule in the positive rule set and discards a change if it evaluates to TRUE for at least one rule in the negative rule set. The negative rule set is evaluated before the positive rule set.

This section contains these topics:

• Specifying a Positive Rule Set for a Propagation

• Specifying a Negative Rule Set for a Propagation

BEGIN
  DBMS_PROPAGATION_ADM.ALTER_PROPAGATION(
    propagation_name  => 'strm01_propagation',
    rule_set_name     => 'strmadmin.strm02_rule_set');
END;
/

BEGIN
  DBMS_PROPAGATION_ADM.ALTER_PROPAGATION(
    propagation_name        => 'strm01_propagation',
    negative_rule_set_name  => 'strmadmin.strm03_rule_set');
END;
/

Adding Rules to the Rule Set for a Propagation

To add rules to the rule set of a propagation, you can run one of the following procedures:

• DBMS_STREAMS_ADM.ADD_TABLE_PROPAGATION_RULES

• DBMS_STREAMS_ADM.ADD_SUBSET_PROPAGATION_RULES

• DBMS_STREAMS_ADM.ADD_SCHEMA_PROPAGATION_RULES

• DBMS_STREAMS_ADM.ADD_GLOBAL_PROPAGATION_RULES

Excluding the ADD_SUBSET_PROPAGATION_RULES procedure, these procedures can add rules to the positive rule set or negative rule set for a propagation. The ADD_SUBSET_PROPAGATION_RULES procedure can add rules only to the positive rule set for a propagation.

This section contains these topics:

• Adding Rules to the Positive Rule Set for a Propagation

• Adding Rules to the Negative Rule Set for a Propagation

BEGIN
  DBMS_STREAMS_ADM.ADD_TABLE_PROPAGATION_RULES(
    table_name              => 'hr.locations',
    streams_name            => 'strm01_propagation',
    source_queue_name       => 'strmadmin.strm_a_queue',
    destination_queue_name  => 'strmadmin.strm_b_queue@dbs2.example.com',
    include_dml             => TRUE,
    include_ddl             => TRUE,
    source_database         => 'dbs1.example.com',
    inclusion_rule          => TRUE);
END;
/

BEGIN
  DBMS_STREAMS_ADM.ADD_TABLE_PROPAGATION_RULES(
    table_name              => 'hr.departments',
    streams_name            => 'strm01_propagation',
    source_queue_name       => 'strmadmin.strm_a_queue',
    destination_queue_name  => 'strmadmin.strm_b_queue@dbs2.example.com',
    include_dml             => TRUE,
    include_ddl             => TRUE,
    source_database         => 'dbs1.example.com',
    inclusion_rule          => FALSE);
END;
/

Removing a Rule from the Rule Set for a Propagation

You remove a rule from the rule set for an existing propagation by running the REMOVE_RULE procedure in the DBMS_STREAMS_ADM package. For example, the following procedure removes a rule named departments3 from the positive rule set of a propagation named strm01_propagation.

BEGIN
  DBMS_STREAMS_ADM.REMOVE_RULE(
    rule_name        => 'departments3',
    streams_type     => 'propagation',
    streams_name     => 'strm01_propagation',
    drop_unused_rule => TRUE,
    inclusion_rule   => TRUE);
END;
/

In this example, the drop_unused_rule parameter in the REMOVE_RULE procedure is set to TRUE, which is the default setting. Therefore, if the rule being removed is not in any other rule set, then it will be dropped from the database. If the drop_unused_rule parameter is set to FALSE, then the rule is removed from the rule set, but it is not dropped from the database even if it is not in any other rule set.

If the inclusion_rule parameter is set to FALSE, then the REMOVE_RULE procedure removes the rule from the negative rule set for the propagation, not the positive rule set.

To remove all of the rules in the rule set for the propagation, then specify NULL for the rule_name parameter when you run the REMOVE_RULE procedure.

Removing a Rule Set for a Propagation

You remove a rule set from a propagation using the ALTER_PROPAGATION procedure in the DBMS_PROPAGATION_ADM package. This procedure can remove the positive rule set, negative rule set, or both. Specify TRUE for the remove_rule_set parameter to remove the positive rule set for the propagation. Specify TRUE for the remove_negative_rule_set parameter to remove the negative rule set for the propagation.

For example, the following procedure removes both the positive and the negative rule set from a propagation named strm01_propagation.

BEGIN
  DBMS_PROPAGATION_ADM.ALTER_PROPAGATION(
    propagation_name         => 'strm01_propagation',
    remove_rule_set          => TRUE,
    remove_negative_rule_set => TRUE);
END;
/

Dropping a Propagation

You run the DROP_PROPAGATION procedure in the DBMS_PROPAGATION_ADM package to drop an existing propagation. For example, the following procedure drops a propagation named strm01_propagation:

BEGIN
  DBMS_PROPAGATION_ADM.DROP_PROPAGATION(
    propagation_name      => 'strm01_propagation',
    drop_unused_rule_sets => TRUE);
END;
/

Because the drop_unused_rule_sets parameter is set to TRUE, this procedure also drops any rule sets used by the propagation strm01_propagation, unless a rule set is used by another Oracle Streams client. If the drop_unused_rule_sets parameter is set to TRUE, then both the positive rule set and negative rule set for the propagation might be dropped. If this procedure drops a rule set, then it also drops any rules in the rule set that are not in another rule set.