1z0-076 Sample Questions Answers

In the context of Oracle Data Guard and container databases (CDBs) managed by Data Guard Broker:

• All broker actions execute at the root container for container databases (D): When using Data Guard Broker to manage a CDB, the actions performed by the broker are executed at the level of the root container. This is because the root container maintains the control and configuration information that applies to the entire CDB, including all of its pluggable databases (PDBs).
• After a role change, the broker opens all Pluggable databases (PDBs) on the new primary (E): Following a role transition such as a switchover or a failover, Data Guard Broker ensures that all PDBs within the CDB of the new primary database are opened, which is essential to resume operations of the PDBs without manual intervention.References:
• Oracle Data Guard Broker documentation
• Oracle Multitenant Administrator'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

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.

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.

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​​.

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.

• 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

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​​​​.

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.

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.

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.

The DBMS_ROLLING package facilitates a rolling upgrade process across a Data Guard configuration. The START PLAN procedure in particular handles several critical actions, including:

• Creating a guaranteed restore point on the standby databases (B): This ensures that the standby databases can be reverted to their state before the rolling upgrade process in case of any issues.
• Building a LogMiner dictionary on the primary database instance (C): This is necessary for logical standby databases to interpret redo data during the SQL Apply process.
• Creating a guaranteed restore point on the primary database (D): Similar to the standby databases, this ensures that the primary database can be reverted to a known good state if necessary.References:
• Oracle Database PL/SQL Packages and Types Reference
• Oracle Data Guard Concepts and Administration Guide

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

• A static service must be registered with the local listener to enable DGMGRL to restart instances during the course of broker operations (A): For DGMGRL (Data Guard Manager Command-Line Interface) to perform instance management operations, such as restarting instances, a static service registration in the listener is required. This allows the broker to connect to the database instance even when the instance is not fully up and the dynamic service registration is not available.
• Installing the oracle-database-preinstall-19c package is NOT sufficient to set up operating system kernel parameters for Oracle Net (C): While the oracle-database-preinstall-19c package automates the setting of several kernel parameters to meet the preinstallation requirements for Oracle Database, it does not specifically tailor all settings for Oracle Net in a Data Guard configuration. Additional manual configuration may be required to optimize Oracle Net services for Data Guard operations.

References:

• Oracle Data Guard Broker documentation
• Oracle Net Services Administrator's Guide

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 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

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 ​​.