1z0-076 Questions and Answers

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

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.

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 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.

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.

References:

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

• DB_NAME (A): The name of the database, which should remain consistent across the primary and standby databases.
• db_file_name_convert (C): This parameter helps define the mapping of data file names from the primary to the standby database, which is crucial during the creation and operation of a standby database.
• COMPATIBLE (D): The compatibility level can influence the features that can be used on the standby database and must be consistent with or higher than that of the primary database, especially after upgrades.
• STANDBY_ARCHIVE_DEST (F): This parameter specifies the destination of archived redo log files on the standby database, which is important for log transport and apply services.

References:

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

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.

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

To enable Fast-Start Failover in a Data Guard environment, the following conditions must be in place:

• The Data Guard environment must be managed by the Data Guard Broker (A): The Broker simplifies management tasks and is required to enable fast-start failover, which is an automatic failover mechanism provided by Data Guard.
• You can specify only one standby database as the fast-start failover target (C): Fast-start failover is designed to fail over to a single, predetermined standby database, known as the target standby.
• Flashback Database must be enabled on both the primary database and the Fast-Start Failover target standby database (F): Flashback Database provides a quick way to revert a database to a point in time before a logical or physical corruption or error occurred. It must be enabled on both the primary and target standby databases to allow for the possibility of reinstating the old primary as a standby after a failover.References:
• Oracle Data Guard Concepts and Administration Guide
• Oracle Database High Availability Overview

Data Guard Broker is a management tool that simplifies the configuration, management, and monitoring of Data Guard environments. The prerequisites for using Data Guard Broker include:

• The primary and standby databases must run the same version of the Oracle Database server (A): This ensures compatibility between the primary and standby databases and enables seamless role transitions and data synchronization.
• Network connectivity to the primary database instance must be defined on the servers hosting the standby database instances (B): Proper network connectivity is essential for communication between the primary and standby databases, allowing for the replication of data and the synchronization of changes.
• If any database in the configuration is a RAC database, then the broker configuration files must reside in shared storage accessible by all database instances for all databases in the broker configuration (D): In Real Application Clusters (RAC) environments, shared storage ensures that all instances of the RAC database can access the broker configuration files, facilitating the management of the Data Guard environment across all instances.References:
• Oracle Data Guard Broker documentation
• Oracle Real Application Clusters Administration and Deployment Guide

• 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

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

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.

References:Oracle Data Guard Concepts and Administration documentation provides detailed explanations of different redo transport modes and their implications on data protection and performance. Asynchronous transport mode's behavior and association with Maximum Performance mode are outlined explicitly.

C. The LGWR (Log Writer) process is responsible for writing redo entries from the redo log buffer to the online redo log files on the primary database. This is a fundamental process in the Oracle Database architecture, ensuring that all changes made to the database are captured for purposes such as recovery, replication, and high availability.

D. Real-time apply on a logical standby database requires standby redo log files. The standby redo log files are used to store redo data received from the primary database before it is applied to the logical standby database. This enables the logical standby to apply changes as they are received, without waiting for the current redo log file to be archived.

E. Similarly, on a physical standby database, standby redo log files are used for real-time apply. They store redo data from the primary database, allowing the physical standby to apply redo data concurrently as it is received, rather than waiting for redo log files to be archived. This capability is crucial for maintaining a physical standby database that is closely synchronized with the primary database with minimal lag.

These functionalities are integral to Oracle Data Guard configurations and are not dependent on Oracle Streams or Oracle GoldenGate, which are separate technologies for data replication and integration​​​​.

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.

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.