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

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.

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.

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.

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.

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.

WhenSTANDBY_FILE_MANAGEMENTis set toAUTO, 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.

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.

The ORA-03172: STANDBY_MAX_DATA_DELAY error indicates that the real-time query on the physical standby database is experiencing delays beyond the specified maximum data delay threshold. Increasing the network bandwidth (Option E) can enhance the speed at which redo data is transferred from the primary to the standby database, thereby reducing the likelihood of exceeding the STANDBY_MAX_DATA_DELAY threshold. Reducing I/O latency on the primary database's storage (Option B) ensures that redo data is generated and shipped more efficiently, further mitigating the risk of delay. These actions, focused on optimizing data transfer and processing speed, address the root causes of the ORA-03172 error in a synchronous Data Guard configuration operating in Maximum Availability mode.

TheEDIT DATABASE...SET PARAMETERcommand 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') .

Enterprise Manager Cloud Control provides a graphical interface to manage multiple standby databases, simplify switchovers and failovers, and automate failover processes to a specified target standby database. It offers a comprehensive view and control over the Data Guard configuration, making complex operations more manageable.

DGMGRL is a command-line tool specifically designed for managing Data Guard configurations. It allows the administration of multiple standby databases, simplifies the execution of switchovers and failovers, reinstatements, and conversions to and from snapshot standby databases, and supports the automation of failover processes to a specified standby database.

Other options like RMAN, SQL*Plus, CRSCTL, SRVCTL, and GDCCTL do not provide the same level of integrated management functionality for Data Guard environments as Enterprise Manager Cloud Control and DGMGRL.

A snapshot standby database is a fully updateable standby database that is created by converting a physical standby database into a snapshot standby database. The main characteristics of a snapshot standby database include:

B: Tablespaces can indeed be dropped in a snapshot standby database because it is updateable and allows all types of DML and DDL operations that do not conflict with the standby role.

C: Tablespaces can be created in a snapshot standby database for the same reasons that they can be dropped; it supports all operations that do not interfere with its standby nature.

E: Tables can be dropped in a snapshot standby database, as it is a fully updateable standby.

Options A and D are incorrect because 'FAILOVER TO' and 'SWITCHOVER TO' commands are not used with snapshot standby databases in these contexts. A failover converts a standby database into the primary role after the original primary has become unavailable, and is not a reversible role transition. Switchover is a planned role reversal between the primary database and one of its standby databases and is not applicable to snapshot standby databases in the context provided.

Option F is incorrect because a logical standby database cannot be converted into a snapshot standby database directly. A logical standby is used for different purposes such as reporting and querying with real-time data, and its structure is different from a physical standby which can be converted into a snapshot standby.

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.

In the context of Oracle Data Guard and Global Database Services (GDS):

DGMGRL may be used to add the Sales configuration to the Prod pool in gds (A):Data Guard Broker's command-line interface DGMGRL can be utilized to manage configurations with GDS, allowing the addition of Data Guard Broker configurations to GDS pools.

Performing a role change with DGMGRL automatically notifies GDS which in turn activates the appropriate services (B):When a role change is executed using DGMGRL, GDS is automatically notified, and it then activates the services that are appropriate for the new database roles.

In Oracle, a sequence created with theGLOBALkeyword is available and can produce values across all sessions and instances. However, a sequence created with theSESSIONkeyword is only specific to the session it was created in. When theNEXTVALis 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:

Theasequence is global, which means it is available across the entire database, including the standby database with Real-Time Query enabled. So, when session 2 callsa.nextval, it will get the next value in the sequence, which is 21 since session 1 already retrieved 1.

Thebsequence is session-specific, so when session 2 callsb.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 beaoutput as 21 andboutput as 1, which corresponds to Option C.

Transaction Guard provides benefits in terms of transaction consistency and recovery in a Data Guard environment:

It provides application continuity by rolling back uncommitted transactions interrupted by a failover or switchover (B):Transaction Guard ensures that any uncommitted transactions at the time of an outage are rolled back consistently, thus preserving the integrity of the application's data and state.

Asynchronous redo transport is a method where the primary database does not wait for an acknowledgment from the standby database before committing transactions, which helps in minimizing the impact on the primary database's performance (B). This transport mode is associated with the Maximum Performance data protection mode, which prioritizes performance over synchronicity of data between the primary and standby databases (C). While it provides a level of data protection, there could be some data loss in the event of a primary database failure because redo data may not have been transmitted to the standby database at the time of the failure.

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

ThefastStartFailoverTargetproperty is not set onDogs(A):The primary database (Dogs) needs to have a fast-start failover target configured for the operation to succeed.

TheLogXptModeproperty is set toASYNConSheepwhileSheepis the target standby database (B):Fast-start failover requires synchronous redo transport (SYNCorFASTSYNC) to ensure zero data loss, which is a prerequisite for enabling the feature.

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.

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.

Logical standby databases allow the execution of DDL and DML operations, which makes them suitable for maintaining bitmap indexes and materialized views without affecting the performance of the primary database .

Logical standby databases can be used for performing rolling upgrades and patching with minimum downtime, meeting another requirement .

They also enable the testing of new application software releases against an up-to-date replica of the primary database, fulfilling the last requirement.

Other configurations involving physical standby databases or combinations of logical and physical standby databases might not meet all the specified requirements as efficiently or with the same level of performance isolation for the primary database.