If automatic reinstatement fails, the broker will log errors and the former primary database will remain in the mounted state. The previous examples dealt with setting up only one service on a database. You must set both If the Broker configuration is changed to make a bystander the new failover target (probably a good idea if the failed database will be down for a while), the observer will not automatically reinstate the former primary because it is no longer part of the FSFO configuration. The subcommands for this verb include start, stop, setMaster, show, and delete_alternate_observer. Make some new changes and verify that they are preserved after failover. SHOW ObserverConfigFile used to check the runtime property ObserverConfigFile. These are the actions the broker performs after you start a complete failover. The Make sure everything is working before moving on. For systems with multiple RAID controllers, consider creating SRLs such that their IO is balanced across the controllers. In a Data Guard environment primary database is open in read write mode and the standby database in read only mode for reporting purpose. 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. fast-start failover operation, the observer checks if a fast-start failover When the conditions for fast-start failover are met, the Broker adds messages to the observer log and broker log indicating that fast-start failover would have been initiated. A fast-start failover occurred because a user-configurable condition was detected or was requested by an application by calling the DBMS_DG.INITIATE_FS_FAILOVER function. Add an entry to the oratab file for the standby, db1:/u01/app/oracle/product/11.1.0/db_1:Y. On Linux/Unix, the directory specified by the DG_ADMIN environment The value specified for either of these properties should allow the master observer to connect to any instance of an Oracle RAC database. This method will disable fast-start failover on all databases in the broker configuration. See Setting the Protection Mode for Your Configuration. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. Commands For Managing Observers on Multiple Configurations. The foundation of FSFO is Data Guard - a primary and at least one standby. LinkedIn:https://www.linkedin.com/in/hari-prasath-aa65bb19/ You will then need to re-create the physical standby databases from a copy of the new primary database before you can reenable them. The time interval specified by the FastStartFailoverThreshold property is ignored if the master observer detects that a user-configurable condition has occurred or if a fast-start failover has been requested by the DBMS_DG.INITIATE_FS_FAILOVER function. LGWR is unable to write to any member of the log group because on an I/O error. 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. The role change is directed to the same standby database that was specified for the FastStartFailoverTarget database property on the primary database. Application Continuity is supported for Oracle Data Guard switchovers to physical standby databases. The FastStartFailoverTarget configuration property on the primary unless the new property value contains the current fast-start failover target. The Marketplace image that you use to create the VMs is Oracle:Oracle-Database-Ee:12.1..2:latest. The guide attempts to be operating system agnostic; however, some examples may contain platform specific elements such as path and file naming conventions. services. If the DG_ADMIN environment variable is not defined, or the fast-start failover has not occurred to the target standby database. Figure 6-1 shows the relationships between the primary database, target standby database, and observer during fast-start failover: Before Fast-Start Failover: Oracle Data Guard is operating in a steady state, with the primary database transmitting redo data to the target standby database and the observer monitoring the state of the entire configuration. By default the file is named fsfo.dat and is created in the working directory where the observer is started. Worked as a Development and Database Administrator. Subsequent changes to the same block during the same snapshot are not recorded. Being FSFO ready means that all conditions are met for a successful failover, including having a running observer and sufficient redo transmitted to the failover target to meet durability requirements. However, you can change the name or the location of the file if you start the observer using the DGMGRL START OBSERVER command and include the FILE IS qualifier. If you have an Oracle RAC primary database, consider specifying a higher value to minimize the possibility of a false failover in the event of an instance failure. This list describes conditions in which the broker cannot automatically reinstate the former primary database. In the restore stage, Flashback Database restores the database to a point prior to the standby_became_primary_scn using the before-image blocks in the Flashback Database logs. SQL> Select Database_role from v$Database; After a failover, the broker publishes Fast Application Notification (FAN) events. Initiate the failover on the standby database STAN: If local_listener is already in use, add the Data Guard listener to the list. Download Ebook Oracle 11g 12c Data Guard With Asm Lab Practice A Complete Hands On Lab Practice To Manage A Data Guard . The OberverPingRetry property specifies the number of FastStartFailoverLagLimit If both the observer and designated standby database lose connectivity with the primary database for longer than the number of seconds specified by the FastStartFailoverThreshold configuration property, the observer will initiate a fast-start failover to the standby database. What is true about data guard set up with fast-start failover (FSFO) in Oracle Cloud Infrastructure (OCI)? In the following example, a service named sales is configured to be active in the PHYSICAL_STANDBY role on the primary database NORTH. At this point, you can either: Disable fast-start failover (described in Disabling Fast-Start Failover) and attempt to open the former primary database, Manually reinstate the former primary database, as described in Reenabling Disabled Databases After a Role Change. fsfo_postcallout are stored in the same location as files to automate tasks that must be performed before and after a fast-start failover 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). environment variable must have exclusive permissions wherein it can be accessed only However the target can receive redo from a far sync instance.). Change the failover target to the standby being switched over to, Change the failover target to the desired standby. Displays when the primary and target standby databases are synchronized and the configuration is operating in maximum availability mode. fast-start failover through Cloud Control. The platform provides comprehensive services such as maintaining and monitoring databases to help the oracle databases in surviving during data corruption. specified by the ObserverPingInterval property. Thus, the command-line prompt on the observer computer does not The broker verifies the state and status of the databases to ensure that the switchover transitioned the databases to their new role correctly. STAN is now transitioned to the primary database role.Now your PHYSICAL STANDBY Database has become PRIMARY. For more details about managing Redo Apply services using properties, see Managing Log Apply Services. present, you must start the observer manually using the following The broker allows a complete failover to proceed as long as there are no errors present on the standby database that you selected to participate in the failover. the primary database and the target standby database do not have a network FAN events are published using Oracle Notification Services (ONS) for all Oracle integrated database clients in Oracle Database 12c and later. Fast-start failover is inhibited in this case. You can perform a manual failover even if fast-start failover is enabled. The FastStartFailoverThreshold time interval starts when the observer first detects there might be a failure with the primary database. PDBs. Managed recovery process has been stopped between primary and standby database and standby becomes primary database. An alternative is to enable flashback database on the primary (and the standby if desired) so in the event of a failover, the primary can be flashed back to the time before the failover and quickly converted to a standby database. For Active Oracle Data Guard, it will fail to open up a connection unless its in read-only mode. For switchovers, understanding all of the factors can simplify the choice of which standby database to consider as your new primary database. Dataguard Configuration details:- Login in to Standby Server:- Step:1 Check the database role and open_mode Select name,open_mode,database_role from v$database; Step:2 Cancel the MRP process alter database recover managed standby database cancel; Step:3 The below commands will help to bring up standby as primary Immediate Failovers in Configurations Using Cascaded Standbys. Start the observer by running dgmgrl and logging in using SYS credentials. The broker never automatically reinstates the former primary database if a fast-start failover was initiated because a user configuration condition was detected or was requested by an application calling the DBMS_DG.INITIATE_FS_FAILOVER function. The Oracle Database 11g observer can make use of specific credentials, allowing the same wallet to be used for multiple observers with different SYS passwords. You can create two callout configuration scripts, a Getting the Oracle Net configuration right is one of the key factors in a successful FSFO deployment. Otherwise, they must be re-created from a copy of the new primary database. the names of the scripts created in the previous step. created under this directory by DGMGRL will also have the same permissions. The simple tests described in this guide are fine for making sure the basics are working, but you'll probably want to develop a more comprehensive set of tests suited to your environment and requirements. The word manual is used to contrast this type of failover with a fast-start failover (described in Fast-Start Failover). Oracle Database 10g allows a different password file to be used as long as the SYS passwords are the same on the primary and standby. This is the recommended method for disabling fast-start failover. You must re-create the database manually from a copy of the current primary database and then reenable the database in the broker configuration. On the Data Guard Failover Confirmation page, specify the type of failover that you want to perform: Complete: All available redo is applied on the standby database. issue commands and interact with the broker configuration. In addition to setting the configuration protection mode to maximum performance, you will also need to ensure that the LogXptMode database property for both the primary and target standby database is set to ASYNC. This It is very much useful, when the organization has multiple standby sites. Note: Data Guard requires dedicated server connections for proper operation. Dataguard broker is used to automate monitoring and controlling standby setups. Database services can be configured to be active in specific database roles on Oracle RAC databases and on single-instance databases managed by Oracle Restart. (Snapshot standbys are not included in the table because they are not supported as fast-start failover targets.). Fast-start failover allows the broker to automatically fail over to a previously chosen standby database in the event of loss of the primary database. Keep this trigger as simple and reliable as possible, limiting it to only what is absolutely necessary at the moment of role transition, since any failures at this point may affect availability. To start an observer, you must be able to log in to DGMGRL with an account that has SQL>ALTER SYSTEM SWITCH LOGFILE; Running a StatusReport on the primary should verify that the error is due to a missing observer. DGConnectIdentifier, "Scenario 9: Performing a Switchover Operation" for an example of using the VALIDATE DATABASE command to show a database's readiness to complete a role switchover, "Scenario 10: Performing a Manual Failover Operation" for an example of using the VALIDATE DATABASE command to show a database's readiness to complete a role failover. If the switchover transitions a logical standby database to the primary role, then: The original primary database will be switched to a logical standby role. Stores the observer runtime data file and observer configuration file in directory does not have the required permissions. the observer was killed after the stall began, but before the failover timeout had elapsed). During a complete failover, the broker performs the failover steps described in How the Broker Performs a Complete Failover Operation. If all the databases do not have the same values, SRVCTL attempts to override the values, which will fail on the physical standby database because it is open read-only. If the protection mode was at maximum protection, it is reset to maximum performance. Create a script to automate FSFO failover initiation and use it as your standard method for standby flips. Databases that can be reinstated will have the following status value: For the REINSTATE command to succeed, Flashback Database must have ERROR: Unable to verify the graphical display setup. upheld. Switchover Steps. STANDBY>ALTER DATABASE OPEN; RAM). However, failover is attempted if the ObserverOverride configuration property is set to TRUE. Since the observer is a specialized instance of a dgmgrl session, the observer host should be installed with either the Oracle Client Administrator software or the full Oracle Database software stack. The minimum value is 100 milliseconds. In such a case, no attempt is made to transmit any unsent redo from the cascader to the terminal standby. To start an immediate failover, use the DGMGRL FAILOVER TO database-name IMMEDIATE command. To stop the observer, see Stopping the Observer. Don't initiate failover unless at least 30 minutes of history is available. This can happen for either of the following reasons: A bystander standby database has applied more redo data than the new primary database itself had applied when it was a standby database. When you run commands that need access to the observer An observer process is integrated in the DGMGRL client-side component of the broker and typically runs on a different computer from the primary or standby databases and from the computer where you manage the broker configuration. See the Oracle Maximum Availability Architecture technical briefs at: When setting the FastStartFailoverLagLimit configuration property, consider these tradeoffs between performance and potential data-loss: A low lag limit will minimize data loss but may impact the performance of the primary database. Reinstatement will have to be accomplished by other means (manual or scripted Broker commands). Any apply delay must be removed before beginning a switchover. Immediate: No additional data is applied on the standby database, resulting in a data-loss . 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. In fact, failovers are so reliable, fast, and simple that switchovers become the exception rather than the rule. groups used by multiple configuration commands. When using Maximum Availability mode, consider lowering this to reduce the time commits block when the standby becomes unavailable. See the START OBSERVER Broker stores it configuration information in a mirrored set of files outside the database. Step:1 Check the database role and open_mode Performing a Manual Failover Task 1: Determine Which of the Available Standby Databases is the Best Target for the Failover, Performing a Manual Failover Task 2: Start the Failover, Performing a Manual Failover Task 3: Reset the Protection Mode, Performing a Manual Failover Task 4: Re-establish a Disaster-Recovery Configuration. Theoretically, this method can be used when a data guard failover occurred between the primary and standby database, but not a switchover. In the event of a The same thing happens if a shutdown and startup of either database occurs - the service that is started is the one that matches the role of the database being started. 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. Note: if the observer loses contact with the primary, but the standby does not, the observer can determine that the primary is still up via the standby. Flashing back a database is much faster and more seamless (one simple DDL statement) than traditional point-in-time or SCN-based recovery. Step:6 For example, if the old standby was a physical or snapshot standby, then the old primary must be re-created as a physical standby. Steps for FAILOVER the Dataguard environment By default, both files are stored in $ORACLE_HOME/dbs. Your email address will not be published. This is typically done for planned maintenance of the primary system. ObserverConnectIdentifier allows you to specify different connect identifiers for the observer to use. The following is an example of setting the LogXptMode property: Alternatively, use the RedoRoutes property to set the redo transport mode for the target standby and database that is currently in the primary role. In order to accommodate all load conditions, Oracle recommends having at least one more SRL group than the number of ORL groups of the same size. Bystander standby databases that are not disabled by the broker after the switchover will continue operating in the state they were in before the switchover. This is normal. Issue the following SRVCTL commands: Now the correct services are running on the correct databases. Reenabling Disabled Databases After a Role Change describes how to do this. The example assumes that the standby uses the same directory structure as the primary. This article - the seventh in this ongoing . configuration file exists. Before stopping an observer, note the following: The observer does not stop immediately when you issue the STOP OBSERVER command. In Maximum Availability mode, FSFO guarantees that no transaction that has received a commit acknowledgment will be lost during a failover. With increased latency comes decreased throughput; however, in some cases the difference in throughput may be made up by increasing parallelism. If failover is not possible for some reason, then the master observer will continue checking whether the standby database is ready to fail over. restart the new physical standby database. That is, if the observer is connected to any instance in the Oracle RAC, all instances will show a value of YES. 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. FSFO enabled configurations having multiple standbys cannot switchover to a standby that is not the failover target. As a result, there is no guarantee that the observer will not perform a fast-start failover to the target standby database if the observer determines that conditions warrant a failover. If the PreferredObserverHosts property is set for the current To verify the observer is started and the configuration is ready for If the FastStartFailoverPmyShutdown configuration property is set to TRUE, then the former primary database will have been automatically shut down and must be manually restarted before the master observer can attempt to reinstate it. The primary database must be running in order to start the observer. 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. second. SUSPENDED is cleared when connectivity with the primary database is restored. If the value is non-zero, failover is possible any time the standby database's apply With a value of TRUE for this property, the primary will shut down after being stalled for the number of seconds specified by the FastStartFailoverThreshold property. The commands that can be executed for a group of configurations (as declared in an observer configuration file) are as follows. To stop it, you can do either of the following: Choose the Stop Observer option on the first page of the fast-start failover wizard and click Continue at the bottom of the page. If there is more than one standby database in the configuration, you must explicitly set the FastStartFailoverTarget property on the primary database to name one or more candidate target standby databases. Written by authors well-known for their talent with RAC, Pro Oracle Database 11g RAC on Linux . To prevent automatic reinstatement of the former primary database in these cases, set this configuration property to FALSE. By default, the observer will initiate failover to the target standby if and only if ALL of the following are true: Oracle Database 11g Rel 1 introduced user configurable failover conditions that can trigger the observer to initiate failover immediately. The observer is very lightweight, requiring few system resources. It may be possible to convert the old Primary into a Standby database now instead of having to do a time consuming duplicate again.
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