5 Managing Members of a DG PDB Broker Configuration

Learn how to manage DG PDB broker configurations and monitor the state of DG PDBs.

Note:

The only supported protection mode for DB PDB configurations is maximum performance mode.

This chapter contains the following topics:

• Managing Broker Configuration Members
• Managing States of Broker Configuration Members
• State Transitions for DG PDBs
• Managing Database Properties in DG PDB Configurations
• Monitoring Redo Transport for DG PDBs
• Viewing Transport Lag and Apply Lag
• Monitoring a DG PDB Configuration
• Querying Database Status in DG PDB Configurations

Managing Broker Configuration Members

The broker uses information in its configuration files to manage and monitor the state of members in the DG PDB configuration.

The COMPATIBLE initialization parameter in the source database and the target database must be set to 21.1 or higher.

Tasks performed for CDB configurations such as setting configuration properties, creating configuration files, starting Data Guard broker, and enabling or disabling broker configurations are also applicable to DG PDB configurations.

Note:

Although you can configure a DG PDB for a PDB that is part of a CDB that already has a standby database, a role change between such a PDB and its DG PDB results in an inconsistent PDB configuration between the primary and standby databases. Similarly, a role change between the primary and standby database will result in the DG PDB being orphaned because it no longer has a source PDB. When you use Data Guard broker to manage the Data Guard primary and standby databases, creating a DG PDB in such a scenario is not allowed.

When Data Guard broker is not used to manage the Data Guard environment, it is recommended to avoid setting up a PDB for Data Guard protection when the container to which the PDB belongs already has a Data Guard standby database.

Managing States of Broker Configuration Members

The standby PDBs in a DG PDB configuration can be in the APPLY-ON or APPLY-OFF state.

Standby PDBs in a DG PDB configuration can be in the APPLY-ON or APPLY-OFF state as describe in the following table.

Table 5-1 Database States and Descriptions in DG PDB Configurations

Database role	State Name	Description
Target PDB	APPLY-ON	Redo Apply is started on the target PDB within the target configuration. If this is an Oracle Real Application Clusters (Oracle RAC) instance, redo apply is started only on the instance where the command is run. The PDB cannot be opened if recovery is running. If the PDB is open when the command to start recovery is run, the PDB is closed.
Target PDB	APPLY-OFF	Redo Apply is stopped on the target PDB.

State Transitions for DG PDBs

Use the DGMGRL EDIT DATABASE command to explicitly change the state of a standby PDB. You can only change the state of the entire database, including all its PDBs.

The EDIT PLUGGABLE DATABASE command is used to change the state of a standby PDB. For example, the following command changes the state of the target standby nyc_sales to APPLY-OFF:

DGMGRL > EDIT PLUGGABLE DATABASE 'target-prim' SET STATE = 'APPLY-OFF';
Succeeded.

Managing Database Properties in DG PDB Configurations

Database properties of members in a DG PDB configuration are of two types: monitorable properties or configurable properties.

Use monitorable properties to view run-time information related to configuration members. Monitorable properties can be viewed only when the member is enabled. Use the SHOW DATABASE VERBOSE command to list all monitorable properties. Use the SHOW DATABASE command to view details about a particular property. Use the SHOW PLUGGABLE DATABASE command to view information about the source PDB or target PDB.

Configurable properties impact the operation or configuration of a database. Use configurable properties to view and dynamically update information related to configuration members. You can edit properties regardless of the member's state. If the member is disabled when a property is edited, the property value takes effect after the member or configuration is enabled, as appropriate.

Use the EDIT DATABASE command to update the properties of the source database or target database. Use the EDIT PLUGGABLE DATABASE command to update the state of a source PDB or target PDB.

The SHOW DATABASE command has been enhanced to display information about Data Guard at the PDB level. In a DG PDB configuration, the SHOW DATABASE output shows whether the database has any source or target PDBs, and the number of PDBs in each role.

Example 5-1 Displaying the Properties of a Source Database (SHOW DATABASE output)

DGMGRL> SHOW DATABASE boston;
 
Database - boston
  Role: PRIMARY
  Intended State: TRANSPORT-ON
  Redo Rate:           (unknown)
  PDB Data Guard Role: SOURCE 
  Data Guard Source PDB(s): 1
  Instance(s):
    boston
  
  
Database Status:
SUCCESS

Example 5-2 Displaying the Properties of Individual PDBs (SHOW PLUGGABLE DATABASE output)

This example uses the SHOW PLUGGABLE DATABASE command to display information about the target PDB nyc_sales.

DGMGRL> show pluggable database nyc_sales at newyork;

Pluggable database - NYC_SALES at newyork

  Data Guard Role:     Physical Standby
  Con_ID:              3
  Source:              con_id 3 at boston
  Transport Lag:       0 seconds (computed 0 second ago)
  Apply Lag:           14 seconds (computed 0 second ago)
  Intended State:      APPLY-OFF
  Apply State:         Not Running

Pluggable Database Status:
SUCCESS

Monitoring Redo Transport for DG PDBs

The broker automatically starts redo transport services between a source database and target database once there has been at least one PDB designated for replication.

Viewing Transport Lag and Apply Lag

Transport lag is a measure of the degree to which redo transport has not shipped redo data from the source database to the target database. Apply lag is a measure of the degree to which redo apply has not applied the redo that has been received at the target database.

The redo transport service transmits redo data from the source database to the target database. The log apply services at the individual target PDB updates the target PDB with this redo data, thereby keeping the target PDBs consistent with the source PDBs. Each target PDB has its own log apply service. The archived redo log files and standby redo log files contain all of the database changes except for unrecoverable or unlogged changes.

Transport Lag

The transport lag is displayed in the output of the SHOW PLUGGABLE DATABASE command. This lag represents, in seconds, the amount of redo data that has not been received by the target CDB for the specified DG PDB.

Average Apply Rate

If the Apply State is Running, the average apply rate is displayed in the output of the SHOW PLUGGABLE DATABASE command. The average apply rate pertains to a specific DG PDB.

Monitoring a DG PDB Configuration

Monitor the status of the configuration and its members to view statistics, diagnostic information, detect problems, and quickly take necessary actions.

After a DG PDB configuration is enabled, the broker schedules an automatic health check on the individual members. It monitors and reports problems with redo transport and recovery progress. Diagnostic information is written to the broker log files (drc*.log) and can be viewed using DGMGRL commands.

Querying Database Status in DG PDB Configurations

Use DGMGRL to query information about the DG PDB configuration and its members.

You can view the status of the DG PDB configuration and detailed information about the source database and target database.

Example 5-3 Displaying Information for a DG PDB Configuration

The commands below can be used to display information about a DG PDB Configuration:

DGMGRL> SHOW CONFIGURATION;

Configuration - Boston

  Protection Mode: MaxPerformance
  Members:
  boston  - Primary database
    newyork - Primary database in NewYork configuration 

Data Guard for PDB:   Enabled in SOURCE role

Configuration Status:
SUCCESS   (status updated 7 seconds ago)

DGMGRL> SHOW ALL PLUGGABLE DATABASE AT boston;

PDB Name         PDB ID   Data Guard Role    Data Guard Partner

BOS_SALES           3     Primary            NYC_SALES (con_id 3) at newyork
BOS_ACCT            4     None               None
BOS_FINANCE         5     None               None

DGMGRL> SHOW ALL PLUGGABLE DATABASE AT newyork;

PDB Name         PDB ID   Data Guard Role    Data Guard Partner

NYC_SALES           3     Physical Standby   BOS_SALES (con_id 3) at boston