data guard failover steps

These FAN events can be used in the following ways: Applications can use FAN without programmatic changes if they use one of these Oracle integrated database clients: Oracle Database JDBC, Oracle Database Oracle Call Interface (OCI), Oracle Data Provider for .NET ( ODP.NET), or Universal Connection Pool for Java. The advanced way is in the following article: Connect-Time Failover by a Dynamic Service Name. A database in the primary role will not open until it has verified with the observer that it is still the primary. RMAN also copies the spfile and password files and you can change the values for individual parameters. For Fast Connection Failover (FCF) to occur, a client must be able to locate the new primary database after a failover. This configuration property causes the former primary database to be automatically reinstated if a fast-start failover was initiated because the primary database was either isolated or had crashed. This section describes how to configure an Oracle Net connect descriptor that meets this requirement. There can be up to four observers for a single Data Guard configuration. irrespective of its content, indicates that the script executed successfully. Displays only on the target standby database when either the primary or target standby database was shut down in a controlled fashion (using the NORMAL, IMMEDIATE, or TRANSACTIONAL, options, but not the ABORT option). See Prerequisites for more information. If you have not used the SET ObserverConfigFile command after starting the current DGMGRL client, then the result will always be: ObserverConfigFile=observer.ora. For more details about managing redo transport services using database properties, see Managing Redo Transport Services. The broker preserves the protection mode that was in effect prior to the failover. In this case, the primary database stalls and prevents any further transactions from If groups are not defined, you can still operate on all configurations defined in the file as a whole. It wouldn't be much of a test if we didn't verify that our durability constraints were being met, so let's make a change on the primary and see if it survives the failover. For this reason, you should first issue this command on the target standby database. Errors occurring for any other configuration members will not impede the switchover. In this mode, the FastStartFailoverLagLimit configuration property is set to a non-zero value. Reinstate the former primary database as a new standby database. The "Configuring Authentication" chapter of the Oracle Database Security Guide provides detailed instructions for creating a wallet. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. For each temporary table, verifying that temporary files associated with that table on the primary database also exist on the standby database. Nothing will ruin your day faster than finding out that the standby the observer just failed over to is 12 hours behind in applying redo. lower detection times for primary database failures, you must When the primary database and the target standby database regain network connectivity, the broker will disable fast-start failover for the entire broker configuration. Immediate Failovers in Configurations Using Cascaded Standbys. Immediately after issuing command in step 2, shut down and restart the standby instance STAN: To move the observer to another computer: There is no need to disable fast-start failover when you move the observer. about starting the observer as a background When the primary database and the (non-target) standby database regain network connectivity, the broker will propagate its current fast-start failover setting (ENABLED or DISABLED) to the non-target standby. primary, only the observers specified in the property can be use in the SET time, if all the sessions that are connected though the active services To start an observer as a background process, use the DGMGRL Displays if the standby database's redo applied point does not lag the primary database's redo generation point by more than the number of seconds specified by the FastStartFailoverLagLimit configuration property and the configuration is operating in maximum performance mode. The Marketplace image that you use to create the VMs is Oracle:Oracle-Database-Ee:12.1..2:latest. In maximum protection mode, set the LogXptMode database property to SYNC (note that in maximum protection mode, a far sync instance cannot be used to ship redo to a standby). The primary database must be running in order to start the observer. Transitions the target standby database into the primary role, opens the new primary database in read/write mode, and starts redo transport services. The default group is all the configurations defined in the observer configuration file. This may result in data loss. For reliable startup, the initial connection should always be made to the primary. When this property is set to NONE, the broker will disable all bystander standby databases without checking whether they have applied more redo data than the new primary database. This function can be called from a connection to either the primary or any standby in the configuration. Sets up redo transport from the new primary to the other members of the configuration, Starts Redo Apply services on the new standby, Ensures the other standbys in the broker configuration are viable to the new primary, Integrates with Oracle Clusterware and Oracle Global Data Services (GDS) to ensure that the proper services are started after a role change. Note that enabling FSFO does not make the configuration ready for automatic failover - that requires an observer, which we'll get to next. 1 second. Only the observer can initiate FSFO failover. Starting Observers as Background Processes. CONNECT command. This nomination is noted in the observer log file and in the broker log file (drc*.log). A normal shutdown uses SHUTDOWN NORMAL, SHUTDOWN IMMEDIATE, or SHUTDOWN TRANSACTIONAL. callout directory. Displays when the target standby database does not have all of the primary database redo data and the configuration is operating in maximum availability mode. To run an observer as a background process, use the DGMGRL command START OBSERVER IN BACKGROUND. Fast-start failover quickly and reliably fails over the target standby database to the primary database role, without requiring you to perform any manual steps to invoke the failover. If the configuration is not failable, the DBMS_DG.INITIATE_FS_FAILOVER function returns an ORA error number (it does not signal an exception) informing the caller that a fast-start failover could not be performed. Alternatively, if you intend to switch back to the original primary relatively soon, then you may re-enable the disabled standby databases after the switch back. Disabling fast-start failover without the FORCE option can succeed only if the database on which the command is issued has a network connection with the primary database and if the primary database and target standby database have a network connection. command on the observer computer: The observer is a continuously executing process that is Bounce your database and verify database name its open mode and its role: SQL> shutdown immediate; ORA-01109: database not open Database dismounted. An immediate failover should only be performed when a complete failover is unsuccessful or in the error cases just noted. milliseconds and that of ObserverRetryCount is 10. Broker changes database parameters during startup and role transitions via ALTER SYSTEM commands. configuration scripts and checks for errors or misconfigurations. If there is another standby database that is available for failover, you can perform a manual failover to that standby database after you first disable fast-start failover using the FORCE option on that standby database. observer and the others are backup observers. FSFO can also be used with logical standbys and an FSFO-enabled configuration may have multiple standbys with a mix of physical and logical, but only one standby can be the failover target at any given time. However, fast-start failover cannot occur when the target standby database is in an unobserved state. If you initiated a complete failover and it fails, you might need to use immediate failover. The standby VM (myVM2) has the Oracle software installed only. Use the wrapper script to start the observer process when the observer host boots or to restart it if it dies. Queries and DML will continue to run - only sessions that commit will block. In previous releases, OCI and ODP.NET clients receive FAN notifications via Oracle Advanced Queuing (AQ). If you like a connect-time failover to survive across a data guard switchover, you need another way to do it. An application should use caution when calling the DBMS_DG.INITIATE_FS_FAILOVER function because the observer will initiate failover, if at all possible. Set this property for the primary and target standby database if you want the observer to use a different connect identifier than that used to ship redo data (that is, the connect identifier specified by the DGConnectIdentifier property). FB Page:https://www.facebook.com/dbahariprasath/? environment variable must have exclusive permissions wherein it can be accessed only If failover is not possible for some reason, then the master observer will continue checking whether the standby database is ready to fail over. Rather, fast-start failover will be enabled in accordance with the current protection mode. The primary database, it attempts to disable fast-start failover on as many databases in the configuration with which it has a network connection. The broker first converts the original primary database to run in the standby role. For each broker configuration on which one or more When querying the V$DATABASE view, pay special attention to the following: The FS_FAILOVER_STATUS column, which can contain the values described in Table 6-2. Note that these properties only affect whether primary shutdown and automatic reinstatement are performed if a fast-start failover occurs because the primary crashed or was isolated from the observer and target standby database. STOP OBSERVING [cfg_group_name] stops LOCAL observers running on this host (where this DGMGRL is running) for all broker configurations in a specified group. been enabled on the database prior to the failover and there must be sufficient Note: If you have just enabled archivelog mode, force an archive log creation ( alter system archive log current) to ensure that at least one archive log exists. FAN events are published using Oracle Notification Services (ONS) for all Oracle integrated database clients in Oracle Database 12c and later. Before beginning a failover, first determine that there is no possibility of recovering the primary database in a timely manner, and ensure that the primary database is shut down. It's good practice to use separate listeners for application connections and Data Guard connections. fast-start failover, you can issue the DGMGRL SHOW FAST_START FAILOVER, Client-side broker 5. The minimum For a system to process an instruction involving data access, these are the certain steps involved: Fetch the block of data from the hard disk (secondary/permanent storage) to the primary memory (e.g. observer immediately begins monitoring the status and connections to Note that the value of the FastStartFailoverPmyShutdown configuration property must be FALSE for the primary to stall indefinitely under these conditions. Waits for the target standby database to finish applying any unapplied redo data before stopping Redo Apply (if the target is a physical standby database) or SQL Apply (if the target is a logical standby database). Broker will validate the configuration, set parameters on both databases, and start managed recovery. You can switch back to the original primary and then either retry the switchover to the original target standby, or choose another standby in the configuration to switch over to. Restore - Flashback Database restores the datafiles to the closest snapshot prior to the specified SCN. Issue the following commands on Primary database and Standby database to find out: This not only saves time and minimizes problems by automating an otherwise manual process, it exercises your failover and DR procedures with every flip so that you know the FSFO configuration is sound and, in a real emergency, everyone knows what to do. Disabling fast-start failover with the FORCE option when connected to the target standby database guarantees that fast-start failover will not occur. Bystander standby databases can be shut down at any time in any order without impacting fast-start failover. This can be compared to performing an RMAN restore of the datafiles from a backup taken prior to the specified SCN, but is much faster. Create a trigger on this event to perform actions specific to your environment after a switchover or failover, such as updating the name resolution service to point to the new primary. Logical standby databases that are disabled during failover can be reinstated. A simple example for *nix is provided below that will work with both releases. In this mode you will need to consider how much data loss is acceptable in terms of seconds and set the FastStartFailoverLagLimit configuration property accordingly. November 20, 2009. command does not have a network connection to the primary database. If a bystander standby database is not disabled by the broker during this failover, it will remain in the state it was in before the failover. Note that the new primary database does not need to be restarted. failure on the primary database. lag is less than or equal to the value specified by the Once you have completed the switchover back to the original primary, you may then reenable the physical and snapshot standby databases since they are still viable standbys for the original primary database. If one of these errors has occurred, follow the guidelines in "Resolving ORA-752 or ORA-600 [3020] During Standby Recovery" in My Oracle Support Note 1265884.1 before proceeding. Data Guard broker publishes this service on each instance as it comes up and broker management of the instance is initialized: To patch an environment where the Observer is running and fast-start failover is enabled, follow these steps prior to applying the patch. Then the STOP OBSERVER command can be issued successfully on the former master observer. Therefore, the detection time can be reduced to nearly There is no data loss during a switch-over. It will also alert you to databases that have had Flashback Database disabled at some point after FSFO was enabled. directory specified by this variable does not exist, or the directory does not have the If you want to use one Oracle home to start multiple observers, with each observer monitoring a different fast-start failover configuration, use the FILE qualifier to specify a unique observer configuration file location for each configuration to be monitored. database (if real-time query is enabled). Subdirectories within When performing a switchover in a configuration whose standby databases are Use Cloud Control or DGMGRL to perform either a complete (recommended) or an immediate failover. The only exception to this is failovers to snapshot standby databases. A complete failover can occur without any data loss, depending on the destination attributes of redo transport services, but an immediate failover usually results in some data loss. FSFO enabled configurations having multiple standbys cannot switchover to a standby that is not the failover target. We'll leave the other properties at their default values for the walkthrough, but you should become familiar with all of the Broker config and database properties. If the primary database has multiple standby databases, then you can specify multiple fast-start failover targets, using the FastStartFailoverTarget property. A switchover guarantees no data loss and is typically done for planned maintenance of the primary system. The broker verifies the state and status of the databases to ensure that the switchover transitioned the databases to their new role correctly. broker opens all the PDBs on the new primary database and on the target standby The Data Guard broker and the secondary database both run the observer and observe the primary database for downtime. An observer can be moved from one computer to another through a process of stopping it on one system and and re-starting it on another. Reinstate or re-create standby databases in the configuration that were disabled by the broker. Remote login is required, along with a password file, to allow the databases in a Data Guard configuration to connect to each other. multiple, inexpensive servers is the basis for the failover and other fault-tolerance features that RAC provides. MASTEROBSERVERHOSTS, DGMGRL reports an error if the While Oracle 11g's Data Guard definitely protects a database when the entire production site is lost via its failover capabilities, it's still necessary for an Oracle DBA to intervene to complete the failover process. RAM). A good method to determine Flashback Database storage requirements is to enable Flashback Database and observe the amount of storage it uses during several peak loads. Running a StatusReport on the primary should verify that the error is due to a missing observer. 1. Verify the configuration from both hosts. first recording that a fast-start failover cannot happen. If the new primary database was a primary database in the past, and had block You can find detailed information about all observers, including master observers and backup observers, in the V$FS_FAILOVER_OBSERVERS view. The rest of this section provides examples of using DGMGRL SHOW commands to display fast-start failover information and includes sections describing the following views: The DGMGRL SHOW FAST-START FAILOVER command displays all the fast-start failover related information. To allow the master observer to automatically reinstate the former primary database, the database must be started and mounted. database is in the primary role. During a complete failover, the broker performs the failover steps described in How the Broker Performs a Complete Failover Operation. To avoid problems due to timing variations, values less than 60 minutes are not recommended and values of 30 or less virtually guarantee Flashback Database failure. See Reenabling Disabled Databases After a Role Change. These conditions are described in the following table: Dictionary corruption of a critical database. process. A single-instance database must be registered with Oracle Restart in order to publish FAN events via ONS. The primary database was shut down without using the ABORT option. If you want the broker to skip this viability check of bystander standby databases during a complete failover, thus decreasing the overall failover time, set the BystandersFollowRoleChange configuration property to NONE. Oracle Data Guard Broker is a utility that can help you manage your Oracle Data Guard. milliseconds. FastStartFailoverLagLimit property. Displays on the primary database after loss of connectivity to the target standby database and the change to the UNSYNCHRONIZED state (maximum availability mode) or to the TARGET OVER LAG LIMIT state (maximum performance mode) cannot be confirmed by either the target standby database or the observer. This document only talks about switchover involving physical standby database. Choosing the standby database with the smallest transport lag can minimize the amount of data loss and in some cases, incur no data loss at all. For example, perform full level 0 backups weekly and incremental level 1 backups daily. When a fast-start failover occurs because either a user configurable fast-start failover condition is detected or an application initiates a fast-start failover by calling the DBMS_DG.INITIATE_FS_FAILOVER function, the former primary database is always shut down and never automatically reinstated. For switchovers, understanding all of the factors can simplify the choice of which standby database to consider as your new primary database. configuration property. Switching over to a logical standby database results in the snapshot and physical standby databases in the broker configuration being disabled by the broker, making these databases no longer viable as standby databases. connectivity with target standby. The physical and snapshot standby databases will have to be re-created from a copy of the new primary database. Standby databases not involved in the switchover (known as bystander standby databases) continue operating in the state they were in before the switchover occurred and will automatically begin applying redo data received from the new primary database. A fast-start failover to the target standby database fails. If errors occur during the disable operation, the broker returns an error message and stops the disable operation. When this command is issued, the actual Prerequisites for Enabling Fast-Start Failover provides complete information about all of the fast-start failover and reinstatement requirements. For Oracle Database Release 12.2 and higher, Oracle Enterprise Manager Cloud Control (Cloud Control) supports configuring multiple observers using the Enterprise Manager Command Line Interface (EM CLI). Figure 6-2 The Observer in the Fast-Start Failover Environment. The new primary database starts transmitting redo data to the new standby database. The targets are referred to as candidate targets. In case of primary database failure, you will need to perform failover to transition the standby database to the primary role. However the target can receive redo from a far sync instance.). The required attributes vary depending on your configuration (including whether your environment is Oracle RAC-based or single-instance). In the following example, ObserverReconnect is set to 30 seconds. ObserverConfigFile is a DGMGRL session runtime property. In such a case, no attempt is made to transmit any unsent redo from the cascader to the terminal standby. Automatic failover quickly and reliably fails over the standby Autonomous database to the primary database role, without requiring you to perform any manual steps. An spfile is required to persist these changes. They must be re-created from a copy of the new primary database. Clusterware: The broker notifies Oracle Clusterware to stop active Starting with Oracle Database Release 21c, use the DG_ADMIN Manual failover to the fast-start failover target can be performed without receiving an acknowledgement from the observer. The example below takes advantage of the 11g RMAN Active Database Duplication feature.

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