1z0-076 Oracle Database 19c: Data Guard Administration Questions and Answers

After a successful switchover operation in a Data Guard environment, the new primary database (the former standby) will be open read-write (option A). If the former primary database transitions to a logical standby database, it will also be open read-write (option C), allowing it to apply redo data while servicing read-only queries. The former primary, if converted to a physical standby, will adopt the state that the former physical standby database was in prior to the switchover, which can vary based on the configuration prior to the switchover (option D). The state of a physical standby database can range from mounted to open read-only, depending on whether Real-Time Query was enabled. Thus, the exact state will depend on the pre-switchover setup. It's also essential to highlight that options B and E suggest specific states for a former primary turned logical standby, and a former primary turned physical standby, respectively, but these states are not fixed and depend on the configurations set up by the database administrators.References:The answers are corroborated by Oracle's documentation on Data Guard switchovers, specifically in the Oracle Data Guard Concepts and Administration guide, which explains the roles and states of databases in a Data Guard configuration before and after switchovers.

DB_NAME (A):The name of the database, which should remain consistent across the primary and standby databases.

db_file_name_convert (C):This parameter helps define the mapping of data file names from the primary to the standby database, which is crucial during the creation and operation of a standby database.

COMPATIBLE (D):The compatibility level can influence the features that can be used on the standby database and must be consistent with or higher than that of the primary database, especially after upgrades.

STANDBY_ARCHIVE_DEST (F):This parameter specifies the destination of archived redo log files on the standby database, which is important for log transport and apply services.

The rate of SQL apply on a logical standby database can be influenced by:

A: The number ofPREPARERprocesses (which seems to be a typographical error and should read asPREPARERor similar) which prepare the redo data for the applier processes.

B: The number of coordinator processes on the standby database instance which coordinate the SQL apply activities.

C: The number of full table scans performed by SQL apply since full table scans can be resource-intensive and slow down the apply rate.

E: The number of applier processes which apply the redo data to the logical standby database.

Option D is incorrect as the size of the undo tablespace on the logical standby database is more likely to affect the SQL apply lag rather than the rate of SQL apply.

Option F is incorrect because the size of the shared pool would typically not influence the rate of SQL apply. The shared pool is more related to the caching of shared SQL and PL/SQL code and control structures.

AWR collects, processes, and maintains performance statistics for problem detection and self-tuning purposes. In an Active Data Guard environment, where the physical standby database can be used for read-only workloads, AWR can be instrumental in identifying performance bottlenecks and areas for optimization. It provides detailed reports that include wait events, time model statistics, and active session history, making it an invaluable tool for tuning SQL queries and overall database performance in an ADG setup.

A fast recovery area must be configured (B):Flashback Database requires a fast recovery area to be set up because flashback logs are stored there. The fast recovery area is a unified storage location for all recovery-related files and activities.

The database must be in ARCHIVELOG mode (C):Flashback Database operation relies on the ability to archive redo logs. Therefore, the database must be running in ARCHIVELOG mode for Flashback Database to be enabled.

In the context of Oracle Data Guard and container databases (CDBs) managed by Data Guard Broker:

All broker actions execute at the root container for container databases (D):When using Data Guard Broker to manage a CDB, the actions performed by the broker are executed at the level of the root container. This is because the root container maintains the control and configuration information that applies to the entire CDB, including all of its pluggable databases (PDBs).

Based on Oracle Database 19c: Data Guard Administration documents, the three measures that can prevent clients from connecting to the wrong database instances during switchovers, failovers, or regular operations in a Data Guard environment are:

B. The standby database services must be defined statically with the Listeners running on the standby database hosts.

D. The client applications must use the correct TNS entries when requesting connections to the database instances.

E. Client TNS entries for the databases use the correct service names for the intended service.

In an Oracle Data Guard configuration, correctly configuring Oracle Net Services (including TNS entries and listeners) is crucial for ensuring that clients connect to the appropriate database instance, whether it's the primary or standby. Defining services on the standby database and associating them with listeners ensures that client applications can connect to the standby when needed, especially useful in a role transition or when the standby is open for read-only access or real-time query. It's essential that TNS entries used by client applications specify the correct service names that correspond to the intended database roles, such as primary or standby. This setup facilitates seamless connectivity to the appropriate instance based on the role, especially critical during switchovers and failovers when the roles of the databases change.

TheRECOVER STANDBY DATABASE FROM SERVICEcommand in RMAN is designed to automate various steps required to recover the standby database, especially when dealing with an archive gap. When this command is executed, the following actions can occur automatically:

Remember all data file names on the standby (1):RMAN has the capability to recall the names and paths of all data files associated with the standby database.

Restart standby in nomount (2):The standby database can be automatically restarted in the NOMOUNT state, allowing recovery operations to proceed without the database being open.

Restore controlfile from primary (3):RMAN can restore the control file from the primary database to the standby system, ensuring that the standby has the most up-to-date control file.

Mount standby database (4):After restoring the control file, the standby database is mounted to prepare for data file recovery.

Rename data files from stored standby names (5):Not typically done automatically by this command.

Restore new data files to new names (6):New data files added to the primary since the last synchronization can be restored to the standby with their correct names.

Recover standby (7):Finally, RMAN will apply any necessary redo logs to bring the standby database up to date with the primary.

While some steps, such as renaming data files (5), typically require manual intervention or scripting, most of the recovery process can be handled by RMAN automatically, streamlining the recovery of the standby database.

According to the requirements stated:

Zero data loss must be guaranteed despite the loss of any one component:This necessitates synchronous redo transport to at least one standby database (for no data loss).

The primary database must be protected against a regional disaster:This implies that there must be a standby database in a different region.

Performance overhead on the primary should be minimized:This suggests that asynchronous transport should be used where possible to reduce the performance impact on the primary.

Downtime on the primary for any reason must be kept to a minimum:This is indicative of a requirement for a fast failover mechanism, possibly with a fast-start failover (FSFO) and high availability.

Given these requirements, the appropriate option that fulfills all these is:

Option C, where 'prima' is the primary database, 'fs1' is the Far Sync instance in the primary region, and 'physt' and 'physt2' are physical standby databases in the primary and remote regions, respectively. In this configuration:

'prima' is set to send redo to 'fs1' using SYNC to guarantee zero data loss.

'fs1' is set to send redo to 'physt' (local standby) using FASTSYNC, which is a low-latency synchronous transport that is optimized for performance.

The Data Guard configuration's protection mode is set to MAXAVAILABILITY to provide the highest level of data protection that is possible without compromising the availability of the primary database.

This configuration ensures that there is zero data loss even if the primary region is completely lost, maintains performance by limiting the synchronous transport to the local region with a Far Sync instance, and has a remote standby database in a separate region for disaster recovery purposes.

To meet the requirements of automatic failover and the highest level of protection without data loss, the combination of FASTSYNC redo transport mode and Maximum Availability protection mode is appropriate. FASTSYNC ensures that the performance impact on the primary database is minimized while still providing synchronous transport. Maximum Availability protection mode offers the highest level of data protection without compromising the availability of the primary database. In case of a network failure or a standby failure, the primary will not halt, avoiding disruption to the primary database operations.

References

Oracle Data Guard Concepts and Administration guide, which details the different protection modes and their respective levels of data protection and impact on database operations.

Real-Time Query is a feature that allows queries to be run on a physical standby database while it is applying redo data. The relevant truths about it are:

Setting standby_max_data_delay=0 requires synchronous redo transport (A):For the real-time apply feature to function with no data delay (zero delay), synchronous redo transport must be used. This setting ensures that the data on the standby database is as current as possible before queries are executed against it.

When issuing a "switchover to sheep;" command in a Data Guard configuration, the primary database (Dogs) transitions to a standby role, and the target standby database (Sheep) becomes the new primary database. Fast-Start Failover (FSFO) remains enabled, but its target changes according to the new roles of the databases. Since Cats is also a physical standby database, it does not become the failover target by default unless it is specified in the broker configuration. After the switchover, the original primary (Dogs) becomes the new standby database and thus the new failover target for FSFO.

D. The database role indicated byFS_FAILOVER_STATUSas BYSTANDER implies that the database is a standby database in the Data Guard configuration. This means the database is neither a primary database nor an active failover target.

E. Since theFS_FAILOVER_OBSERVER_HOSTcolumn showscats, it suggests that this is the host on which the observer would run. However, because theFS_FAILOVER_OBSERVER_PRESENTcolumn is not shown, we cannot definitively state if the observer is currently connected or not. IfFS_FAILOVER_OBSERVER_PRESENTis 'YES', the observer is connected, if 'NO', then it's not. In the absence of this column's output, the best assumption based on the available data is that the observer is not connected.

The output shows that theFS_FAILOVER_STATUSisBYSTANDER, which indicates that the database in question is not actively involved in a fast-start failover configuration as a primary or standby. It is in a bystander role, meaning that while it is part of a Data Guard configuration, it is neither a target for failover nor actively participating in failover operations. Additionally,FS_FAILOVER_OBSERVER_HOSTshows 'cats', which indicates the host where the observer process is expected to run. However, since there is no information about the observer being present, we can infer that although 'cats' is designated for the observer to run, the observer is not currently connected to this database.

References

Oracle documentation on Data Guard configurations and theV$DATABASEview which provides information about the fast-start failover status and observer host.

Creating a physical standby database using RMAN active database duplication requires certain prerequisites to ensure a successful and seamless operation:

Configure Oracle Net connectivity on the primary host to the standby database instance (A):Proper Oracle Net connectivity between the primary and standby servers is essential for communication and data transfer during the duplication process. Oracle Net services provide the network foundation for Oracle Database, Oracle Net Listener, and Oracle applications.

Establish user equivalence for the database software owner between the primary host and standby host (B):User equivalence ensures that the user who owns the Oracle Database software on the primary server has the same privileges on the standby server. This is crucial for RMAN to perform operations on both servers without encountering permission issues.

Enterprise Manager Cloud Control offers comprehensive monitoring capabilities for Oracle Data Guard environments. It enables monitoring the rate at which redo is being applied on a logical standby database (A), which is crucial for ensuring that the standby database is keeping up with the changes from the primary. It also allows setting thresholds on performance metrics, such as the redo generation rate on the primary database (B), to alert administrators when values exceed critical or warning thresholds. Additionally, it provides the capability to estimate the potential data loss in the event of a disaster (E), helping in disaster recovery planning and ensuring business continuity.

When SYNC redo transport mode is combined with Maximum Protection mode, it ensures that no data loss will occur (requirement 1). The physical standby can be converted to a snapshot standby (requirement 2) and later to a logical standby database (requirement 5), satisfying both transformation requirements. Transactions commit as soon as redo data is received by the standby database (requirement 3). The availability of the primary is not dependent on the standby database in Maximum Protection mode, as the primary database will halt if the standby cannot acknowledge the redo (requirement 4), thus indirectly ensuring its availability. It is also possible to deploy Real Application Clusters on both the primary (requirement 6) and the physical standby database (requirement 7), providing high availability and scalability.

References

Oracle Data Guard documentation detailing the requirements for different database roles, protection modes, and redo transport modes, as well as the capabilities and limitations of each configuration.

Synchronous redo transport for zero data loss (B):To guarantee zero data loss in the case of a disaster, synchronous redo transport must be configured between the primary and standby databases.

Conversion to snapshot standby for testing (B):A physical standby database can be temporarily converted into a snapshot standby database to perform real application testing. After testing is completed, the snapshot standby can be converted back to a physical standby to resume its disaster recovery role.

TheDBMS_COMPARISONpackage, used for comparing and converging data objects within a single database or between databases, requires that the databases involved in the block comparison be at least mounted (A). This allows the procedure to access the data blocks for comparison. Additionally, the progress of long-running operations such as block comparison can be monitored using the dynamic performance view V$SESSION_LONGOPS (D), which provides information on the operation's progress and estimated completion time.