Oracle 1z0-076 Oracle Database 19c: Data Guard Administration Exam Practice Test

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.

To reduce the redo apply lag on standby databases, one could increase the size of the standby redo log files. Larger redo log files can accommodate more redo data, which may reduce the frequency of log switches and allow for more continuous application of redo data. Additionally, lowering the DB_BLOCK_CHECKING parameter to MEDIUM or LOW on the standby databases can help improve redo apply performance. High block checking can impose additional CPU overhead during the application of redo data, potentially increasing apply lag times. By reducing the level of block checking, you can lessen this overhead and help reduce the apply lag ​​.

• The command performs a comprehensive set of database checks prior to a role change (A): The VALIDATE DATABASE command in Data Guard Manager (DGMGRL) is designed to perform an exhaustive check of a specified database's readiness for a role change, such as a switchover or failover.
• The command performs network connectivity checks between members of a broker configuration (C): One of the checks includes verifying that the necessary network connectivity exists between the databases in a Data Guard Broker configuration.
• The command can be used for a logical standby database (D): The VALIDATE DATABASE command is versatile and can be used for both physical and logical standby databases to ensure their readiness for role changes.

References:

• Oracle Data Guard Broker documentation
• Oracle Data Guard Concepts and Administration Guide

Far Sync instances are a feature of Oracle Data Guard designed to support zero data loss protection over long distances:

• The Data Guard Broker must be used to deploy and manage Far Sync instances (A): Data Guard Broker simplifies the deployment and management of Far Sync instances, which are an integral part of zero data loss protection configurations.
• They enable standby databases to be configured at remote distances from the primary without impacting performance on the primary (C): Far Sync instances are designed to receive redo from the primary database and then forward it to a remote standby database, thereby avoiding any performance impact on the primary database itself.
• A primary database can ship redo directly to multiple Far Sync instances (E): A primary database can be configured to send redo logs to more than one Far Sync instance, which can then forward the redo to their respective remote standby databases.References:
• Oracle Data Guard Concepts and Administration Guide
• Oracle Database High Availability Overview

• Stop the Observer on host1 to ensure that there are no conflicts between the instances of the Observer running on different hosts.
• Update the Data Guard Broker configuration with the new hostname for the Observer. This step is crucial to redirect the Data Guard Broker to communicate with the Observer on the new host.
• Start the Observer on host2 to resume its operations in the new environment.

Disabling and re-enabling Fast-Start Failover (steps 2 and 4) are not strictly necessary for moving the Observer to a new host. These steps would be more relevant if changes to the configuration of Fast-Start Failover itself were required, which is not the case when simply relocating the Observer.

After a successful failover to the 'cats' database in a Data Guard configuration:

• B: Sheep, being another standby database, would typically remain in the enabled state unless specifically disabled or if there was a configuration issue.
• D: Dogs, which was the primary database prior to failover, will be in a disabled state as part of the failover process. Manual intervention is required to re-establish 'dogs' as a standby database or to return it to the primary role through another role transition.
• E: If the configuration was in Maximum Availability mode before failover, it would remain in this mode after failover, provided all settings were properly configured and no changes were made to the protection mode.

Option A is incorrect because failover does not automatically change the protection mode to Maximum Performance. The protection mode remains as it was prior to the failover unless manually altered.

References: The behavior of Oracle Data Guard during failover and the resulting configuration state is described in the Oracle Data Guard Broker documentation.

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.

A logical standby database is part of Oracle Data Guard and allows the standby database to be open for read-write operations, providing additional flexibility. The requirements met by a logical standby database include:

• Support for workloads requiring additional materialized views (A): Logical standby databases can support materialized views, allowing for complex data summarization and reporting workloads.
• It can be used to create additional tables (C): Unlike physical standby databases, logical standby databases allow for the creation of additional tables that do not exist in the primary database, enabling custom workloads and reporting.
• It can be used for Real Application Testing without affecting the disaster recovery capabilities (E): Logical standby databases can be used to test application changes, patches, and upgrades while still maintaining their role as part of the disaster recovery strategy.
• Support for workloads requiring additional indexes (F): Logical standby databases allow for the creation of additional indexes to optimize query performance for reporting and analytical workloads.References:
• Oracle Data Guard Concepts and Administration
• Oracle Database High Availability Overview

In a Data Guard configuration where the protection mode is set to Maximum Availability and synchronous redo transport is enabled, if the standby destination fails to acknowledge the reception of redo within the net_timeout period, the primary database will terminate the synchronous redo transport mode connections to the standby database to protect the primary database from hanging (C). The primary database then operates in a Maximum Performance mode until the issue is resolved. This behavior ensures that the primary database can continue to process transactions even when the standby database is temporarily unavailable.

References:The Oracle Data Guard Broker documentation and Oracle Data Guard Concepts and Administration guide detail the behavior of different protection modes and the response to network timeouts, including the fallback to asynchronous redo transport to maintain primary database availability.

The error indicates that switching the protection mode to Maximum Protection is not possible due to the presence of a snapshot standby database in the Data Guard configuration, which cannot participate in synchronous redo transport required by the Maximum Protection mode. Therefore, the correct answer is:

• D. Cats is a snapshot standby database.

Comprehensive Detailed Explanation:In an Oracle Data Guard environment, the Maximum Protection mode requires that all redo data be transmitted synchronously to at least one standby database, ensuring no data loss even in the event of a primary database failure. However, a snapshot standby database, by its nature, allows read-write access and is temporarily disconnected from the redo stream, which makes it unable to participate in the synchronous redo transport required by Maximum Protection mode. The presence of a snapshot standby database in the Data Guard configuration thus prevents the activation of Maximum Protection mode, as it cannot guarantee zero data loss without a standby database capable of receiving redo data synchronously.

References:Oracle Data Guard documentation clearly outlines the requirements and restrictions of different protection modes, including the necessity for standby databases to participate in synchronous redo transport to enable Maximum Protection mode. The inability of snapshot standby databases to fulfill this requirement is a key consideration when planning Data Guard configurations and protection levels.

A Far Sync instance is a special kind of Oracle Data Guard configuration that allows synchronous redo transport from a primary database to a remote standby database with minimum impact on the primary database's performance. The Far Sync instance receives redo data synchronously from the primary database (A), then ships it asynchronously to the remote standby database, thus extending zero data loss protection over longer distances and higher network latency environments than would be practical with a synchronous standby alone. The Far Sync instance does not apply the redo data; it just receives and ships it (E). A Far Sync instance does not have data files, and it cannot apply redo to stay synchronized with the primary database.

References:Oracle Database High Availability Overview and Oracle Data Guard Concepts and Administration documentation detail the role and configuration of Far Sync instances, including how they contribute to achieving zero data loss disaster recovery over long distances.

Logical standby databases are a key feature of Oracle Data Guard and offer several distinct advantages, especially in terms of flexibility for reporting, upgrades, and disaster recovery:

• Disaster-recovery solution with switchover and failover options (A): Logical standby databases provide a robust disaster-recovery solution, ensuring that any data updated on the primary database can be recovered. They support both switchover and failover operations, allowing for smooth role transitions between the primary and standby databases.
• Used for reporting workloads requiring additional indexes or materialized views (B): Logical standby databases can be opened for read-write operations and can have additional indexes or materialized views that are not present in the primary database. This makes them ideal for offloading reporting and querying workloads from the primary database.
• Database rolling release upgrades (D): Logical standby databases can be used to perform rolling upgrades of the Oracle Database software. This allows the database to be upgraded with minimal downtime, as the standby database is upgraded first, followed by a switchover to make it the new primary.References:
• Oracle Data Guard Concepts and Administration Guide
• Oracle Database High Availability Overview

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.

D. The database role indicated by FS_FAILOVER_STATUS as 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 the FS_FAILOVER_OBSERVER_HOST column shows cats, it suggests that this is the host on which the observer would run. However, because the FS_FAILOVER_OBSERVER_PRESENT column is not shown, we cannot definitively state if the observer is currently connected or not. If FS_FAILOVER_OBSERVER_PRESENT is '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 the FS_FAILOVER_STATUS is BYSTANDER, 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_HOST shows '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.

ReferencesOracle documentation on Data Guard configurations and the V$DATABASE view which provides information about the fast-start failover status and observer host.

The command ALTER DATABASE FLASHBACK ON; enables the Flashback Database feature, which provides a way to quickly revert an entire Oracle database back to a previous point in time. This command can be executed while an Oracle 19c primary database is either open (option A) or mounted (option B). It is also applicable to an Oracle 19c logical standby database while SQL Apply is active (option E). However, it's important to note that enabling Flashback Database on the primary does not automatically enable it on all associated standby databases, whether they are physical or logical. Each database in a Data Guard configuration must have Flashback Database explicitly enabled if desired. Real Time Query being active on a physical standby does not directly relate to the ability to execute this command on the standby. References: The explanation is based on Oracle's concepts for Flashback Technology and Data Guard configurations as detailed in the Oracle Database Backup and Recovery User's Guide and the Oracle Data Guard Concepts and Administration guide.

To automate the instantiation of a PDB in the standby database after creating a remote clone in the primary database, certain conditions must be met:

• Open PDBI (remote clone source) in Read Only (A): The source PDB from which the clone is created must be open in read-only mode to ensure a consistent state during cloning.
• Set STANDBY_PDB_SOURCE_FILE_DIRECTORY to in the london database (C): This parameter specifies the location on the standby database where the files from the source PDB should be placed.
• Set STANDBY_FILE_MANAGEMENT to auto in the london database (F): This parameter automates the management of file changes on the standby database when structural changes occur on the primary database, ensuring that the clone operation is reflected automatically on the standby.References:
• Oracle Multitenant Administrator's Guide
• Oracle Data Guard Broker documentation

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.

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.

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

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.
• References:Oracle's Data Guard concepts and administration guide provides extensive information on configuring network services for Data Guard environments, ensuring that applications connect to the correct database instance based on the current role of the databases in the Data Guard configuration.

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.

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') .