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.

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.

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.

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.

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

C: Increasing the value for theMAX_SERVERSSQL apply parameter would allow for more applier processes to be initiated, assuming that system resources permit.

D: Increasing thePARALLEL_MAX_SERVERSinitialization 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 theRECOVERY_PARALLELISMparameter controls the number of processes used for instance recovery and media recovery, not for SQL apply.

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.

The SQL apply lag on a logical standby database can be caused by several factors:

A: An undersized undo tablespace can lead to delays in SQL apply operations as it may not be able to handle the volume of undo records generated by the SQL apply process.

B: SQL apply operations that do full table scans can consume significant system resources, potentially leading to higher apply lag.

C: An increased number of bulk updates on the primary database may generate a large volume of redo data, which can cause apply lag if the logical standby cannot apply the changes quickly enough.

F: An undersized shared pool may affect the parsing and execution of SQL statements by SQL apply, which can contribute to the apply lag.

Option D is less likely to be a direct cause of SQL apply lag compared to bulk updates, as inserts generate new data rather than modifying existing data, which SQL apply can typically handle more efficiently.

Option E is incorrect because the size of the standby redo log files on the primary database impacts redo transport lag, not SQL apply lag.

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.

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.

Snapshot standby databases are a feature of Oracle Data Guard that allows a physical standby database to be temporarily converted into a read-write database for testing or other purposes. The true statements about snapshot standby databases are:

FLASHBACK DATABASE is enabled automatically on a snapshot standby database after converting it from a physical standby database if not already enabled (B):When a physical standby is converted to a snapshot standby, FLASHBACK DATABASE is automatically enabled to allow the database to be easily reverted back to its original state.

FLASHBACK DATABASE is enabled automatically on a physical standby database as part of the conversion into a snapshot standby database, if not already enabled (C):As part of the conversion process, FLASHBACK DATABASE is turned on to ensure that changes made while the database is in snapshot standby mode can be undone.

A snapshot standby database may be opened read-write (E):Once a physical standby is converted to a snapshot standby, it can be opened for read-write operations, allowing for testing and other tasks that require a writable database.

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.

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.

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​​.

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.

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 <location of the PDB> in the london database (C):This parameter specifies the location on the standby database where the files from the source PDB should be placed.

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.

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 Physical Standby Database can indeed be converted into a Logical Standby Database, providing flexibility in a Data Guard configuration. This allows for the database to switch roles and supports SQL apply operations, enabling more granular control over the data and transactions being replicated and applied. Additionally, having a configuration with a primary database and one or more physical standby databases allows for rolling upgrades to be performed. This means that each database in the Data Guard configuration can be upgraded in a phased manner, minimizing downtime and ensuring high availability during the upgrade process​​​​.

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.