The execution of the UNSKIP procedure is designed to remove SQL Apply filters that have been previously set up on a logical standby database. Based on the provided statements, the UNSKIP procedure is directed to delete any SQL Apply filters for DML statements associated with objects in the 'HR' schema that start with 'EMP'. Since both SKIP procedures had the same schema name ('HR') and statement type ('DML'), and the UNSKIP procedure uses a wildcard (%) for the object name, it will successfully remove both of the SQL Apply filters for 'EMP_NEW' and 'EMP_OLD', as both object names match the pattern provided in the UNSKIP procedure.

References:Oracle's Data Guard documentation and SQL Language Reference provide insights into managing SQL Apply filters on a logical standby database using the DBMS_LOGSTDBY package. This includes adding and removing filters through SKIP and UNSKIP procedures.

In an Oracle Active Data Guard environment:

• B: Read-mostly reporting applications that utilize global temporary tables to store session-specific data can be effectively offloaded to an Active Data Guard standby database, reducing the load on the primary database.
• C: Sequences can be used with global temporary tables on an Active Data Guard standby database to support certain types of read-mostly applications, though some restrictions on sequence use may apply.
• E: In Oracle Database 19c and later, DML redirection allows DML operations performed on an Active Data Guard standby database to be transparently redirected to the primary database. This is part of the DML Redirection feature.

Option A is incorrect because not all PL/SQL blocks run on an Active Data Guard standby database can be redirected to the primary database. Some PL/SQL executions, specifically those that would attempt to make changes to the database, are not supported on the standby.

Option D is incorrect because DDL operations on private temporary tables are not redirected; instead, private temporary tables are session-specific and are not persisted on disk, so they do not generate redo and are not applicable to an Active Data Guard standby.

References: The behavior and capabilities of Active Data Guard standby databases are documented in the Oracle Data Guard Concepts and Administration guide and the Active Data Guard documentation.

The DBMS_COMPARISON package, 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.

References:Oracle Database PL/SQL Packages and Types Reference provides comprehensive details on the DBMS_COMPARISON package, including its procedures and how to monitor their progress. Additionally, Oracle Database Reference explains the V$SESSION_LONGOPS view, which is commonly used for monitoring long operations in the database.

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.

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.

References:Oracle Enterprise Manager Cloud Control documentation provides extensive information on its monitoring features for Oracle Data Guard, including setting thresholds, estimating potential data loss, and tracking redo apply rates.

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.

References: Oracle Data Guard Concepts and Administration guide details the operations allowed on snapshot standby databases and the processes for transitioning between physical, snapshot, and logical standby databases.

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.
• Disabling Real-Time Query prevents the automatic start of redo apply when a physical standby database is opened read-only (C): If Real-Time Query is disabled, opening the standby database in read-only mode will not start the redo apply process automatically. Redo apply needs to be manually started to synchronize the standby database with the primary.References:
• Oracle Data Guard Concepts and Administration Guide

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.

The command executed (CREATE CONFIGURATION 'DGConfig' AS PRIMARY DATABASE IS 'PROD' CONNECT IDENTIFIER IS PROD;) is used to create a Data Guard Broker configuration named 'DGConfig'. The successful execution of this command depends on several conditions:

• A: The DG_BROKER_START parameter must be set to TRUE on the primary database to start the Data Guard Broker processes. Without the broker processes running, the configuration cannot be created.
• D: Oracle Net connectivity to the PROD database instance must be established on the primary host. This is because the Data Guard Broker requires network accessibility to communicate with the primary database and manage the configuration.
• E: When the configuration is created, the Data Guard Broker configuration files are indeed automatically created in the locations specified by the DG_BROKER_CONFIG_FILEn parameters on the primary database.

It's important to note that the command will not automatically add the PRODSBY1 standby database to the configuration (thus B and C are not correct), and there is no requirement for the standby database to have Oracle Net connectivity defined on the primary host for the execution of this command (making F incorrect as well).

References: This information can be validated in Oracle's Data Guard Broker documentation, which outlines the requirements for setting up and managing a Data Guard configuration using the Data Guard Broker.

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

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.

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

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.

To set up Transparent Application Failover (TAF) in a Data Guard environment with RAC, you would need to:

• On a node of the standby database cluster, execute the srvctl command to add the oltpworkload service for the PRIMARY role (1): This prepares the standby cluster to provide the oltpworkload service in case a failover occurs, and the standby becomes the primary database.
• Make sure clients use the OLTPWORKLOAD service to connect to the database instances (4): This ensures that client connections are directed to the correct service, which is managed by TAF and can fail over in case of a primary database outage.References:
• Oracle Real Application Clusters Administration and Deployment Guide
• Oracle Data Guard Concepts and Administration Guide

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.

In a Data Guard environment, you can offload the backups of certain database components to a physical standby database. Incremental backups of a standby database are interchangeable with the primary database, meaning you can apply a backup taken on a standby database to a primary database and vice versa. This includes control files, data files, and archive logs. Backups of control files and nonstandby control files are interchangeable. You can restore a standby control file on a primary database and a primary control file on a physical standby database, demonstrating their interchangeability and the ability to offload control file backups to one database in a Data Guard environment​​.

Oracle Multi-tenant architecture and Data Guard have several interactions, but specific aspects hold true in such environments:

• The Data Guard broker may be used for multi-tenant databases (B): Data Guard Broker simplifies the management and monitoring of Data Guard configurations and is fully compatible with the Oracle Multi-tenant architecture, allowing for easy management of Data Guard configurations that include multi-tenant container databases (CDBs) and their pluggable databases (PDBs).
• A Data Guard environment with a multi-tenant primary database can operate in any Protection mode (E): Data Guard can be configured to operate in Maximum Performance, Maximum Availability, or Maximum Protection mode, regardless of whether the primary database is a multi-tenant database. This flexibility ensures that Data Guard can meet various data protection and availability requirements in multi-tenant environments.References:
• Oracle Data Guard Broker documentation
• Oracle Multitenant Administrator's Guide

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