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

Global Sequences are Oracle sequences that generate unique values across multiple instances in an Oracle RAC or a Data Guard configuration. Regarding their behavior and performance when connected to a physical standby database with Real-Time Query enabled:

• A: The usage of Global Sequences can indeed have a performance impact on the primary database due to the need to generate unique values that are consistent across both primary and standby databases.
• D: The performance impact on the physical standby database may occur if the CACHE size is too small. This is because the standby database will frequently have to access the primary database to replenish the cache, which can increase the load and potentially lead to performance degradation.
• E: Global Sequences should have the NOORDER and CACHE options set. The NOORDER option ensures that sequence numbers are provided without guaranteeing sequence order, thus improving scalability and performance. The CACHE option is used to specify how many sequence values will be held in memory for faster access.

Option B is incorrect as the LOG_ARCHIVE_DEST_n parameter's definition for standbys pointing back to the primary does not directly pertain to the creation of sequences.

Option C is incorrect because there is no requirement that the size of the cache for a sequence must be at least 100. The CACHE size can be set to a different number based on specific use cases or performance considerations.

References: Oracle's documentation on sequences and their behavior in a Data Guard environment provides insights into the performance considerations and best practices for using sequences, particularly in a Real-Time Query context.

• 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.

References:

• Oracle Data Guard Concepts and Administration Guide
• Oracle Database Testing Guide

The DBMS_ROLLING package facilitates a rolling upgrade process across a Data Guard configuration. The START PLAN procedure in particular handles several critical actions, including:

• Creating a guaranteed restore point on the standby databases (B): This ensures that the standby databases can be reverted to their state before the rolling upgrade process in case of any issues.
• Building a LogMiner dictionary on the primary database instance (C): This is necessary for logical standby databases to interpret redo data during the SQL Apply process.
• Creating a guaranteed restore point on the primary database (D): Similar to the standby databases, this ensures that the primary database can be reverted to a known good state if necessary.References:
• Oracle Database PL/SQL Packages and Types Reference
• Oracle Data Guard Concepts and Administration Guide

Flashback Database is a feature that allows reverting a database to a previous point in time, which is extremely useful in various Data Guard configurations:

• It may be used to flash back a physical standby that receives redo from a far sync instance (C): Flashback Database can be used on a physical standby database to revert it to a past point in time, even when it is receiving redo data from a far sync instance. This can be particularly useful to recover from logical corruptions or unwanted changes.
• You can use it when real-time apply is enabled in case the physical standby suffers from logical corruption (D): Even when real-time apply is enabled, which allows redo data to be applied to the standby database as soon as it is received, Flashback Database can be used to revert the physical standby database to a point in time before the logical corruption occurred.
• It may not be used to flash back a primary database after a failover to a physical standby (E): After a failover has occurred from a primary to a physical standby database, making the standby the new primary, Flashback Database cannot be used to revert the old primary database to a state before the failover because the failover operation makes irreversible changes to the database role and configuration.References:
• Oracle Database Backup and Recovery User's Guide
• Oracle Data Guard Concepts and Administration

For seamless client redirection in a Data Guard environment, the following steps should be taken:

• Create a database service on the primary database that is started automatically by a trigger when the database role is PRIMARY (B): This ensures that the service is only available on the primary database and is automatically started after a role transition due to switchover or failover.
• Modify the connection descriptors used by client applications to include all the standby hosts and connect to the database instance using that service name (B): Client applications use the connection descriptors that include all potential primary hosts (i.e., the current primary and all standbys). This enables clients to connect to whichever database is currently acting as the primary using the service name.References:
• Oracle Data Guard Concepts and Administration Guide
• Oracle Real Application Clusters Administration and Deployment Guide

When setting up a Data Guard Broker configuration for a primary database and its physical standby, the following prerequisites must be met:

• A: Oracle Net connectivity must be defined on both the primary and standby hosts to enable the respective database instances to communicate with each other.
• B: Supplemental logging is required on the primary database because it provides additional logging necessary for the standby database to be able to apply changes from the primary database accurately.
• F: The DG_BROKER_START parameter must be set to TRUE for both the primary and standby database instances. This parameter is used to start the Data Guard Broker process which manages the configuration.

Options C and D are not prerequisites for creating a Data Guard Broker configuration. Additionally, while FORCE LOGGING mode (option E) is recommended as a best practice to prevent possible data inconsistencies during media recovery, it is not a strict prerequisite for creating a Data Guard Broker configuration.

References: This guidance is based on Oracle's best practices for setting up Data Guard configurations, as found in the Oracle Data Guard Broker documentation and the Oracle Data Guard Concepts and Administration guide.

When enabling fast-start failover, certain conditions must be met:

• The fastStartFailoverTarget property is not set on Dogs (A): The primary database (Dogs) needs to have a fast-start failover target configured for the operation to succeed.
• The LogXptMode property is set to ASYNC on Sheep while Sheep is the target standby database (B): Fast-start failover requires synchronous redo transport (SYNC or FASTSYNC) to ensure zero data loss, which is a prerequisite for enabling the feature.
• The LogXptMode property is set to ASYNC on Dogs (D): Similar to the previous point, the primary database must be configured to use synchronous redo transport for the fast-start failover to be possible.References:
• Oracle Data Guard Broker documentation
• Oracle Database Error Messages Guide

The EDIT DATABASE...SET PARAMETER command in Data Guard Management (DGMGRL) is used to modify the value of initialization parameters for a database within a Data Guard configuration. This command can be used to modify both static and dynamic parameters, but if a static parameter is changed, the new value will take effect only after the database is restarted. The database must be up and running for the command to execute, and the values set using the command are directly applied to the specified database (in this case, 'boston') .

To increase the number of applier processes on a logical standby database, the following changes can be made:

• C: Increasing the value for the MAX_SERVERS SQL apply parameter would allow for more applier processes to be initiated, assuming that system resources permit.
• D: Increasing the PARALLEL_MAX_SERVERS initialization parameter would allow for more parallel execution processes, which can be used by SQL apply to increase the number of applier processes.

Option A is incorrect as decreasing the number of archiver processes will not necessarily increase the number of applier processes; these are unrelated components.

Option B is incorrect because the 'FREPARER' processes do not exist, it seems to be a typographical error, and the 'REPARER' is not a valid Oracle process or parameter.

Option E is incorrect because the RECOVERY_PARALLELISM parameter controls the number of processes used for instance recovery and media recovery, not for SQL apply.

References: Oracle Data Guard Concepts and Administration guide details the configuration and tuning of SQL apply-related parameters in logical standby databases.

The Data Guard Monitor (DMON) process is a key component of Oracle Data Guard. It plays a crucial role in managing and monitoring the state of both the primary and standby databases in a Data Guard configuration.

• Performing role transitions when switchover requests are made (A): DMON is responsible for coordinating the switchover process between the primary and standby databases. This involves safely transitioning the roles of the databases to ensure data protection and availability.
• Maintaining information about all members of the broker configuration in binary configuration files (B): DMON maintains detailed information about the databases in the Data Guard configuration, including their roles, states, and network addresses. This information is stored in binary configuration files, which are used by the Data Guard Broker to manage the Data Guard environment.
• Activating role-based services appropriately in the various database instances of the configuration, based on the database role (C): DMON activates services that are appropriate for the role of each database in the Data Guard configuration. For example, it may activate different services on a primary database than on a standby database, based on the specific requirements of each role.References:
• Oracle Data Guard Concepts and Administration
• Oracle Data Guard Broker documentation

In a Data Guard environment, offloading backups to a physical standby database has certain requirements:

• A: Once the primary database is registered in an RMAN catalog, the standby database can also be registered. This allows RMAN to manage backups coherently across both databases and leverage the standby database for backup purposes without interfering with the primary database's workload.
• C: Backups of the standby control file taken while connected to the catalog where the database is registered can be used to restore the control file on the primary database. This ensures that backup metadata is consistent across the Data Guard configuration.

Options B and D are incorrect because there is no strict requirement for the order in which the primary and standby databases must be registered in an RMAN catalog. However, it is a common practice to register the primary database first.

References: The Oracle Database Backup and Recovery User's Guide provides detailed procedures on how to manage RMAN backups in a Data Guard environment, including offloading backups to a standby database.

The RECOVER STANDBY DATABASE FROM SERVICE command 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.

References:

• Oracle Database Backup and Recovery User's Guide
• Oracle Data Guard Concepts and Administration Guide

When STANDBY_FILE_MANAGEMENT is set to AUTO, the Oracle Data Guard automatically creates, deletes, and renames files on the standby database to match the changes made on the primary database. The tasks that lead to the automatic creation of files on the standby include:

• Adding a data file or creating a tablespace (C): When a new tablespace is created or a new data file is added on the primary database, the standby database automatically replicates this action, maintaining structural consistency with the primary database.
• Creating a PDB from the existing PDB within the same CDB (D): Creating a new Pluggable Database (PDB) within a Multitenant Container Database (CDB) on the primary database triggers an automatic creation of the corresponding PDB within the standby CDB.References:
• Oracle Data Guard Concepts and Administration Guide

The process of performing a rolling release upgrade in a Data Guard environment using a logical standby database generally involves these steps:

• Raise the compatibility level on both databases (1): Ensuring both the primary and logical standby databases are operating with the same and correct compatibility level is essential before starting the upgrade process.
• Upgrade the logical standby database (5): Apply the database upgrade to the logical standby first, which allows the primary database to continue serving the workload without interruption.
• Restart SQL Apply on the upgraded logical standby database (2): Once the logical standby has been upgraded, SQL Apply must be restarted to apply the redo data from the primary database, which is still running the earlier version.
• Perform a switchover to the logical standby database (4): After confirming that the logical standby database is successfully applying redo data, perform a switchover to make it the new primary database.
• Upgrade the old primary database (6): With the new primary database now in place, upgrade the old primary database (which is now the new standby) to the new Oracle Database release.
• Start SQL Apply on the old primary database (3): Finally, start SQL Apply on what is now the standby database to synchronize it with the new primary database.References:
• Oracle Data Guard Concepts and Administration Guide
• Oracle Database Upgrade Guide

Block change tracking is a feature that enhances the efficiency of incremental backups by recording changed blocks in a tracking file. When used with Oracle Active Data Guard:

• It starts the RVWR process on the physical standby database instance (A): When block change tracking is enabled on a physical standby database, the Recovery Writer (RVWR) process is initiated. This process is responsible for recording the changes to blocks in the block change tracking file, which is then used to optimize incremental backups.
• It allows fast incremental backups to be offloaded to the physical standby database (E): With block change tracking enabled on the physical standby database, fast incremental backups can be offloaded from the primary database. This reduces the workload on the primary database and utilizes the standby database for backup operations, improving overall system performance and efficiency.References:
• Oracle Database Backup and Recovery User's Guide
• Oracle Active Data Guard documentation

• The compatible parameter on a standby database that is applying redo, must be equal to or greater than the compatible parameter on the primary that is shipping redo to that standby (A): This ensures that the standby database can apply redo from the primary, even after the primary has been upgraded. The COMPATIBLE parameter setting on the standby database should not preclude it from understanding the redo it receives.
• Modifications to the data dictionary on the primary database caused by the upgrade, are applied on a physical standby database (C): When the primary database undergoes a non-rolling upgrade, any resulting data dictionary changes are transmitted through redo data and applied to the physical standby database.

References:

• Oracle Database Upgrade Guide
• Oracle Data Guard Concepts and Administration Guide

Automatic Block Media Recovery can be a significant feature for maintaining data integrity within a Data Guard configuration.

• A corrupt block on the primary database can be automatically recovered, using a block from a standby database with Real-Time Query enabled (A): When a corrupted block is encountered on the primary database, Oracle can automatically replace it with a good block from the standby database where Real-Time Query is enabled, leveraging the standby as a source of good data.
• A corrupt block on the primary database is automatically recovered, using a block from a flashback log from the primary database (E): If a good block version is available in the flashback logs of the primary database, Automatic Block Media Recovery can use it to recover the corrupted block on the primary.References:
• Oracle Database Backup and Recovery User's Guide

In Oracle, a sequence created with the GLOBAL keyword is available and can produce values across all sessions and instances. However, a sequence created with the SESSION keyword is only specific to the session it was created in. When the NEXTVAL is called for a sequence, it will increment according to the sequence's properties set during its creation.

Given the sequence creation statements and the actions performed:

• The a sequence is global, which means it is available across the entire database, including the standby database with Real-Time Query enabled. So, when session 2 calls a.nextval, it will get the next value in the sequence, which is 21 since session 1 already retrieved 1.
• The b sequence is session-specific, so when session 2 calls b.nextval, it will get the value 1 because for this new session on the standby, this is the first time the sequence is being accessed.

Therefore, the output for session 2 will be a output as 21 and b output as 1, which corresponds to Option C.

References: The behavior of global vs session-specific sequences is outlined in Oracle's SQL Language Reference under the CREATE SEQUENCE statement documentation.