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Question 161:
What is the purpose of the V$SYSSTAT view?
A) To show session statistics
B) To display system-wide statistics including cumulative values for various operations
C) To show system parameters
D) To display system status
Answer: B
Explanation:
The V$SYSSTAT view displays system-wide statistics including cumulative values for various operations such as physical reads, logical reads, sorts, parses, executions, and many other metrics that measure database activity since instance startup. This view is essential for performance monitoring, workload characterization, and identifying resource consumption patterns across the entire instance.
Each row in V$SYSSTAT represents one statistic with columns for the statistic number, name describing what is measured, class categorizing the statistic type, and value showing the cumulative count or amount since instance startup. Statistics include counts of operations like user commits and rollbacks, resource usage like CPU time and memory allocations, and wait events like I/O waits and latch gets.
Performance analysis involves comparing V$SYSSTAT values over time to calculate rates and identify trends. Taking snapshots at intervals and calculating differences reveals activity rates during specific periods. For example, comparing physical reads at two points in time and dividing by elapsed seconds calculates the physical read rate during that interval.
Automatic Workload Repository uses VSYSSTATasaprimarydatasource,capturingsnapshotsperiodicallyandstoringhistoricalstatisticsfortrendanalysisandperformancetuning.AWRreportspresentVSYSSTAT as a primary data source, capturing snapshots periodically and storing historical statistics for trend analysis and performance tuning. AWR reports present V SYSSTATasaprimarydatasource,capturingsnapshotsperiodicallyandstoringhistoricalstatisticsfortrendanalysisandperformancetuning.AWRreportspresentVSYSSTAT data in formatted reports showing workload characteristics, resource consumption, and efficiency metrics derived from these statistics.
Option A is incorrect because session statistics are in VSESSTAT,whileVSESSTAT, while V SESSTAT,whileVSYSSTAT shows system-wide aggregated statistics. Option C is incorrect because system parameters are in VPARAMETERandVPARAMETER and V PARAMETERandVSYSTEM_PARAMETER, not VSYSSTAT.OptionDisincorrectbecausesystemstatusinformationcomesfromviewslikeVSYSSTAT. Option D is incorrect because system status information comes from views like V SYSSTAT.OptionDisincorrectbecausesystemstatusinformationcomesfromviewslikeVINSTANCE, while V$SYSSTAT focuses on cumulative statistics.
Question 162:
Which clause in the GRANT command allows the grantee to grant the privilege to other users?
A) WITH GRANT OPTION
B) WITH ADMIN OPTION
C) ALLOW GRANT
D) GRANT PRIVILEGE
Answer: A
Explanation:
The WITH GRANT OPTION clause in the GRANT command allows the grantee to grant the privilege to other users, enabling delegation of object privileges. When a user receives a privilege WITH GRANT OPTION, they can not only use the privilege themselves but also grant it to other users, creating a chain of privilege grants that supports decentralized privilege administration.
This option applies specifically to object privileges like SELECT, INSERT, UPDATE, DELETE on tables and other schema objects. For example, GRANT SELECT ON employees TO user1 WITH GRANT OPTION allows user1 to not only query the employees table but also to grant SELECT on employees to other users. This enables user1 to manage access to the object without requiring DBA intervention.
Revocation implications are important to understand. When a privilege granted WITH GRANT OPTION is revoked from a user, Oracle automatically revokes that privilege from all users who received it through the revoked user’s grants. This cascading revocation ensures that privilege chains remain consistent when intermediate grantors lose their privileges.
Use cases include delegating application schema management to application administrators who need to grant access to objects without full DBA privileges, implementing decentralized security models where schema owners manage their own object access, and supporting multi-tier applications where middle tier users grant privileges to other application components.
Option B is incorrect because WITH ADMIN OPTION applies to system privileges and roles rather than object privileges, though it serves a similar delegation purpose. Option C is incorrect because ALLOW GRANT is not valid Oracle syntax. Option D is incorrect because GRANT PRIVILEGE is not a clause but part of the basic GRANT syntax.
Question 163:
What is the purpose of the TEMPORARY tablespace clause when creating users?
A) To store the user’s permanent data
B) To specify where the user’s temporary segments for sorts and temp tables are created
C) To create temporary user accounts
D) To store temporary table definitions
Answer: B
Explanation:
The TEMPORARY tablespace clause when creating users specifies where the user’s temporary segments for sorts, hash joins, temporary tables, and other operations requiring temporary storage are created. This assignment directs Oracle to allocate temporary space for the user’s operations in the designated temporary tablespace rather than consuming space in permanent tablespaces.
Temporary tablespaces use tempfiles which have different characteristics from regular datafiles including not being fully initialized at creation, not generating redo logs for changes, requiring no recovery since they contain only transient data, and being managed specifically for temporary segment allocation and deallocation. These characteristics make temporary tablespaces efficient for temporary operations.
The syntax CREATE USER username IDENTIFIED BY password DEFAULT TABLESPACE users TEMPORARY TABLESPACE temp assigns the temp tablespace for temporary operations. If no temporary tablespace is specified, the user inherits the database’s default temporary tablespace. Best practices recommend always explicitly assigning temporary tablespaces.
Temporary tablespace groups allow assigning users to a group of temporary tablespaces rather than a single tablespace. Oracle automatically distributes temporary space allocation across group members, balancing load and preventing any single temporary tablespace from becoming a bottleneck. This feature improves concurrency in environments with heavy temporary space usage.
Option A is incorrect because permanent data is stored in the default tablespace, not the temporary tablespace assigned to users. Option C is incorrect because the temporary tablespace assignment does not create temporary user accounts but rather specifies where temporary work space is allocated. Option D is incorrect because temporary table definitions are stored in the data dictionary, not in temporary tablespaces which contain only temporary segment data.
Question 164:
Which view shows information about datafile I/O statistics?
A) V$DATAFILE
B) V$FILESTAT
C) DBA_DATA_FILES
D) V$IOSTAT_FILE
Answer: B
Explanation:
The V$FILESTAT view shows information about datafile I/O statistics including the number of physical reads and writes, total blocks read and written, and I/O timing information for each datafile. This view is essential for identifying I/O bottlenecks, understanding datafile access patterns, and tuning storage configuration to improve performance.
Each row in V$FILESTAT represents one datafile with columns for file number, physical reads count showing how many read operations occurred, physical writes count showing write operations, phyblkrd showing total blocks read, phyblkwrt showing total blocks written, and timing statistics for I/O operations. These cumulative statistics reveal which datafiles experience the most I/O activity.
I/O analysis involves joining VFILESTATwithVFILESTAT with V FILESTATwithVDATAFILE or DBA_DATA_FILES to correlate I/O statistics with datafile names, tablespace assignments, and file locations. This combined view identifies which tablespaces or objects experience heavy I/O, revealing opportunities for optimization through better storage placement, caching strategies, or object reorganization.
Hot spots in storage occur when specific datafiles experience disproportionately heavy I/O compared to others. Identifying hot spots through V$FILESTAT enables remediation strategies like moving heavily accessed objects to faster storage, spreading objects across multiple files to distribute I/O, or implementing partitioning to spread access across multiple partitions in different datafiles.
Option A is incorrect because VDATAFILEshowsdatafilenamesandlocationsbutnotI/Ostatistics.OptionCisincorrectbecauseDBADATAFILESshowsstaticdatafileinformation,notdynamicI/Ostatistics.OptionDispartiallycorrectasVDATAFILE shows datafile names and locations but not I/O statistics. Option C is incorrect because DBA_DATA_FILES shows static datafile information, not dynamic I/O statistics. Option D is partially correct as V DATAFILEshowsdatafilenamesandlocationsbutnotI/Ostatistics.OptionCisincorrectbecauseDBADATAFILESshowsstaticdatafileinformation,notdynamicI/Ostatistics.OptionDispartiallycorrectasVIOSTAT_FILE also provides I/O statistics but in a different format, though V$FILESTAT is the traditional view for this purpose.
Question 165:
What is the purpose of the FORCE keyword when creating views?
A) To force view execution priority
B) To create the view even if the base tables do not exist or the user lacks privileges
C) To force query optimization for the view
D) To force view materialization
Answer: B
Explanation:
The FORCE keyword when creating views creates the view even if the base tables do not exist or the user lacks privileges on those tables, allowing view definition to proceed without all dependencies being satisfied. This capability is useful when views must be created before base objects exist or when deploying views in environments where dependency resolution order is uncertain.
Without FORCE, CREATE VIEW fails if any referenced table does not exist or if the user lacks necessary privileges on base tables. This default behavior ensures view definitions are valid and usable at creation time. FORCE overrides this validation, storing the view definition even though it cannot be queried successfully until dependencies are satisfied.
Use cases include deployment scripts that create all objects in a single pass where views may be defined before their base tables, migration scenarios where view definitions are preserved even though base objects are not yet migrated, and development environments where placeholder views are created before full implementation. In these situations, FORCE prevents deployment failures due to dependency ordering.
The view becomes usable once dependencies are satisfied. After base tables are created or privileges are granted, the view can be queried successfully without modification. Attempting to query a view created with FORCE before dependencies are satisfied results in errors indicating missing tables or insufficient privileges.
Option A is incorrect because execution priority is controlled through query optimization and resource management, not the FORCE keyword in view creation. Option C is incorrect because query optimization is automatic and not controlled by the FORCE keyword. Option D is incorrect because view materialization creates materialized views which are different objects, not controlled by FORCE in regular view creation.
Question 166:
Which parameter controls the location of the audit trail for traditional auditing?
A) AUDIT_TRAIL
B) AUDIT_FILE_DEST
C) AUDIT_LOCATION
D) AUDIT_SYS_OPERATIONS
Answer: A
Explanation:
The AUDIT_TRAIL parameter controls the location of the audit trail for traditional auditing by specifying whether audit records are written to the database audit trail tables, operating system files, or XML files. This parameter determines how audit information is captured and where administrators must look to review audit data.
Parameter values include NONE to disable auditing, DB to write audit records to the database SYS.AUD$ table, OS to write audit records to operating system audit files, DB_EXTENDED to write to the database with additional SQL text, XML to write to XML-formatted files, and XML_EXTENDED to write XML files with SQL text. Each option provides different trade-offs between performance, security, and analysis capabilities.
Database audit trail storage in SYS.AUD$ allows querying audit data using SQL through views like DBA_AUDIT_TRAIL, simplifying analysis and reporting. However, database storage means audit records could potentially be modified by privileged users. Operating system audit trails provide better protection against tampering since database users cannot modify OS files, though analysis requires parsing file formats.
Modern Oracle databases use unified auditing which consolidates audit trails and provides better performance and security. Unified auditing does not use the AUDIT_TRAIL parameter, instead storing all audit records in a dedicated tablespace managed by Oracle. For databases still using traditional auditing, AUDIT_TRAIL remains relevant for configuration.
Option B is incorrect because AUDIT_FILE_DEST specifies the directory for operating system audit files but does not control whether auditing uses database or file storage. Option C is incorrect because AUDIT_LOCATION is not a valid Oracle parameter. Option D is incorrect because AUDIT_SYS_OPERATIONS controls whether administrative operations are audited but does not specify audit trail location.
Question 167:
What is the purpose of the DBMS_ADVISOR package?
A) To provide advisory messages to users
B) To run various advisors including SQL Access Advisor and Segment Advisor
C) To advise on database configuration
D) To provide recommendations for all database operations
Answer: B
Explanation:
The DBMS_ADVISOR package runs various advisors including SQL Access Advisor and Segment Advisor, providing a programmatic interface for executing automated analysis and receiving recommendations for database optimization. These advisors analyze workload patterns, space usage, and access paths to identify opportunities for performance improvement and space management.
SQL Access Advisor analyzes SQL workload and recommends indexes, materialized views, and partitioning strategies to improve query performance. It examines query patterns, identifies frequently accessed data, and suggests physical design changes that would benefit the workload.
Segment Advisor analyzes segment space usage and recommends actions like shrinking segments to reclaim wasted space, reorganizing fragmented segments, and compressing segments for better space efficiency. The advisor identifies segments with significant free space below the high water mark or excessive fragmentation.
The DBMS_ADVISOR package provides procedures for creating advisor tasks, setting task parameters, executing analysis, viewing recommendations, and implementing suggestions. For example, CREATE_TASK creates a new advisor task, SET_TASK_PARAMETER configures analysis options, EXECUTE_TASK runs the analysis, and GET_TASK_REPORT retrieves recommendations.
Integration with Enterprise Manager provides graphical interfaces to these advisors, making them accessible without directly calling DBMS_ADVISOR procedures. However, understanding the package enables automation of advisor execution in scripts, custom analysis workflows, and programmatic access to advisor recommendations for batch processing.
Option A is incorrect because DBMS_ADVISOR does not provide advisory messages to end users but rather runs automated analysis tools for database optimization. Option C is incorrect because configuration advice is one aspect but the package encompasses multiple specialized advisors for different optimization areas. Option D is incorrect because the package focuses on specific optimization areas like access paths and space management rather than all database operations.
Question 168:
Which clause in ALTER TABLE is used to mark a column as unused without immediately dropping it?
A) DROP COLUMN column_name DEFERRED
B) SET UNUSED COLUMN column_name
C) MARK UNUSED column_name
D) DISABLE COLUMN column_name
Answer: B
Explanation:
The SET UNUSED COLUMN clause in ALTER TABLE marks a column as unused without immediately dropping it, allowing the expensive operation of physically removing the column to be deferred to a less busy time. This two-phase approach to column dropping improves availability by quickly making the column inaccessible without the performance impact of immediate physical removal.
The syntax ALTER TABLE table_name SET UNUSED COLUMN column_name marks the column as unused immediately. The column becomes invisible to queries and DML operations, effectively removing it from the table’s logical structure. However, the column’s data remains physically stored in the table until explicitly dropped later using ALTER TABLE table_name DROP UNUSED COLUMNS.
Benefits include faster execution of the initial operation because Oracle only updates metadata without scanning the entire table to remove column data, improved availability because the table remains fully accessible during the SET UNUSED operation, and deferred physical removal allowing the expensive operation to occur during scheduled maintenance windows or off-peak hours when system impact is acceptable.
Use cases include removing columns from large production tables where immediate physical dropping would take too long, situations requiring urgent column removal for security or application reasons where physical removal can wait, and planned maintenance scenarios where columns are marked unused immediately but physical cleanup happens during scheduled downtime.
Option A is incorrect because DROP COLUMN DEFERRED is not valid Oracle syntax; the SET UNUSED mechanism provides deferred dropping. Option C is incorrect because MARK UNUSED is not the correct Oracle syntax. Option D is incorrect because DISABLE COLUMN is not a valid Oracle clause; columns cannot be disabled like constraints.
Question 169:
What is the purpose of the V$SQL_BIND_CAPTURE view?
A) To show all bind variables in SQL statements
B) To display captured bind variable values for SQL statements in the cursor cache
C) To bind variables to SQL statements
D) To capture SQL execution plans
Answer: B
Explanation:
The V$SQL_BIND_CAPTURE view displays captured bind variable values for SQL statements in the cursor cache, providing insight into the actual values used during SQL execution. This information is valuable for troubleshooting performance issues caused by bind variable peeking, understanding how bind variable values affect execution plans, and diagnosing issues where different bind values lead to different performance characteristics.
Oracle captures bind variable values for SQL statements that use bind variables, storing samples of the values in the cursor cache along with the SQL statement and execution plan. V$SQL_BIND_CAPTURE exposes this captured information, showing the bind variable name, position, data type, and captured value. This visibility helps understand what values applications are passing to SQL statements.
The view includes columns for SQL_ID identifying the statement, NAME showing the bind variable name or position, POSITION indicating the bind variable’s position in the statement, DATATYPE showing the data type, and VALUE_STRING containing the captured value converted to string format. Additional columns provide precision, scale, and other data type details.
Bind variable peeking analysis uses V$SQL_BIND_CAPTURE to determine what values Oracle saw when generating execution plans. If a query performs poorly with certain bind values but well with others, examining captured values helps identify whether bind peeking is causing inappropriate plan selection. This diagnosis guides decisions about using bind-aware cursors or adaptive cursor sharing.
Option A is incorrect because the view shows captured sample values, not all possible bind variables or all occurrences of bind variable usage. Option C is incorrect because binding variables to statements is done by applications or developers, not through this view which only displays captured information. Option D is incorrect because capturing execution plans uses different views like V$SQL_PLAN.
Question 170:
Which parameter specifies the default degree of parallelism for operations when parallel execution is enabled?
A) PARALLEL_THREADS_PER_CPU
B) PARALLEL_DEGREE_POLICY
C) DEFAULT_DEGREE
D) PARALLEL_DEGREE_LEVEL
Answer: B
Explanation:
The PARALLEL_DEGREE_POLICY parameter specifies how Oracle determines the degree of parallelism for operations when parallel execution is enabled, controlling whether parallel execution is automatic and how aggressively Oracle applies parallelism. This parameter fundamentally affects parallel execution behavior across the database.
Parameter values include MANUAL requiring explicit parallelism specification through hints or object definitions, LIMITED enabling automatic parallelism only for objects with explicit parallel degree specifications, AUTO enabling automatic parallel execution for qualifying operations based on optimizer cost analysis, and ADAPTIVE combining AUTO behavior with additional features like parallel statement queueing and in-memory parallel execution.
With AUTO or ADAPTIVE, Oracle automatically determines appropriate parallelism for operations based on factors like object size, system resources, and estimated execution cost. This automatic determination eliminates the need for manual parallelism specification while ensuring that parallel execution is applied when beneficial and avoided when overhead would exceed benefits.
The relationship between PARALLEL_DEGREE_POLICY and other parallel parameters affects overall parallel execution behavior. PARALLEL_MIN_TIME_THRESHOLD specifies the minimum estimated execution time for automatic parallelism to be considered. PARALLEL_SERVERS_TARGET sets a soft limit on parallel servers. Together these parameters control when and how much parallelism is applied.
Option A is incorrect because PARALLEL_THREADS_PER_CPU influences parallel execution server allocation but does not set the default degree of parallelism. Option C is incorrect because DEFAULT_DEGREE is not a valid Oracle parameter name. Option D is incorrect because PARALLEL_DEGREE_LEVEL is not an Oracle parameter; PARALLEL_DEGREE_POLICY controls this behavior.
Question 171:
What is the purpose of SQL plan directives in Oracle Database?
A) To direct SQL execution to specific servers
B) To provide additional information to the optimizer about data characteristics and relationships
C) To force specific execution plans
D) To direct SQL statements to specific tablespaces
Answer: B
Explanation:
SQL plan directives provide additional information to the optimizer about data characteristics and relationships that are not captured in traditional statistics, helping the optimizer make better cardinality estimates and execution plan choices. Plan directives address situations where standard statistics are insufficient for accurate optimization, particularly for complex predicates involving column correlations or expressions.
Oracle automatically creates plan directives when it detects misestimates during SQL execution, such as when actual row counts differ significantly from optimizer estimates. These directives record information about problematic predicates or column combinations, guiding the optimizer to use more appropriate estimation techniques like dynamic sampling for similar queries in the future.
Plan directives are stored persistently in the SYSAUX tablespace and shared across SQL statements that reference the same objects and predicates. This sharing means that optimizer learning from one statement’s execution benefits other statements with similar characteristics, improving optimization across the workload without requiring explicit tuning for each statement.
The DBA_SQL_PLAN_DIRECTIVES view shows existing plan directives including the directive type, object information, creation reason, state indicating whether it is usable, and usage count showing how often it has influenced optimization. Administrators can monitor directive effectiveness and manage directives that are no longer beneficial.
Option A is incorrect because directing SQL to specific servers is not the purpose of plan directives; server allocation is controlled by connection management and service definitions. Option C is incorrect because forcing specific plans is accomplished through SQL Plan Management or hints, not plan directives which provide information rather than forcing behavior. Option D is incorrect because tablespace assignment for SQL execution is not controlled by plan directives.
Question 172:
Which view shows information about archived redo log files including their sequence numbers and archive locations?
A) V$ARCHIVED_LOG
B) V$LOG_HISTORY
C) DBA_ARCHIVED_LOGS
D) V$ARCHIVE_DEST
Answer: A
Explanation:
The V$ARCHIVED_LOG view shows information about archived redo log files including their sequence numbers, archive locations, timestamps, and status. This view is essential for monitoring archiving operations, verifying that all logs have been archived successfully, and managing archived log files for backup and recovery operations.
Each row represents one archived log file with columns including SEQUENCE# showing the log sequence number, THREAD# identifying the RAC instance thread in multi-instance configurations, DEST_ID indicating which archive destination received the file, NAME showing the full path to the archived log file, and COMPLETION_TIME indicating when archiving completed. Additional columns show file sizes, block counts, and SCN ranges.
Common uses include verifying that log sequences are complete with no gaps by checking for missing sequence numbers, confirming that all archive destinations received copies of logs, identifying the most recent archived log for recovery planning, determining archived log locations for backup or cleanup operations, and monitoring archiving performance through completion times.
The relationship between online redo logs and archived logs is tracked through VARCHIVEDLOG.Asthelogwriterfillsonlineredologsandswitchestonewlogs,theARCnprocessesarchivethefilledlogs,creatingentriesinVARCHIVED_LOG. As the log writer fills online redo logs and switches to new logs, the ARCn processes archive the filled logs, creating entries in V ARCHIVEDLOG.Asthelogwriterfillsonlineredologsandswitchestonewlogs,theARCnprocessesarchivethefilledlogs,creatingentriesinVARCHIVED_LOG. This tracking ensures visibility into archiving operations and enables verification that archiving keeps pace with redo generation.
Option B is incorrect because VLOGHISTORYprovidesabbreviatedinformationaboutloghistorybutVLOG_HISTORY provides abbreviated information about log history but V LOGHISTORYprovidesabbreviatedinformationaboutloghistorybutVARCHIVED_LOG is more comprehensive for archived log management. Option C is incorrect because DBA_ARCHIVED_LOGS is not a standard Oracle view name. Option D is incorrect because V$ARCHIVE_DEST shows archive destination configuration, not information about specific archived log files.
Question 173:
What is the purpose of the NOMOUNT startup mode?
A) To start the instance without mounting or opening the database
B) To prevent users from connecting
C) To start in maintenance mode
D) To skip database verification
Answer: A
Explanation:
The NOMOUNT startup mode starts the instance without mounting or opening the database, allocating memory structures and starting background processes but not accessing the control file or datafiles. This startup mode is necessary for operations that must occur before the database is mounted, such as database creation or control file recreation.
When you execute STARTUP NOMOUNT, Oracle reads the initialization parameter file, allocates the SGA based on memory parameters, starts background processes like PMON, SMON, DBWn, and LGWR, and makes the instance available for administrative operations. However, the instance does not read the control file or become associated with any specific database at this stage.
Use cases include creating a new database using CREATE DATABASE which requires the instance to be started but not associated with any existing database, recreating control files using CREATE CONTROLFILE when the existing control file is damaged or lost, performing certain RMAN operations that require the instance to be started independently, and troubleshooting scenarios where control file issues prevent normal mounting.
From NOMOUNT mode, you can progress to MOUNT mode using ALTER DATABASE MOUNT to read the control file and associate the instance with the database, and then to OPEN mode using ALTER DATABASE OPEN to open datafiles and make the database fully operational. This phased startup provides control and allows intervention at each stage.
Option B is incorrect because preventing user connections is accomplished through STARTUP RESTRICT, not NOMOUNT mode. Option C is incorrect because maintenance mode typically refers to RESTRICT mode or having the database mounted but not open, not specifically NOMOUNT mode. Option D is incorrect because NOMOUNT does not skip verification but rather stops the startup process before verification would occur during mounting and opening.
Question 174:
Which package provides procedures for managing optimizer statistics preferences and defaults?
A) DBMS_STATS
B) DBMS_OPTIMIZER
C) DBMS_STATISTICS
D) DBMS_STAT_FUNCS
Answer: A
Explanation:
The DBMS_STATS package provides procedures for managing optimizer statistics preferences and defaults including setting global preferences for statistics gathering, setting object-level preferences for individual tables or schemas, managing automatic statistics gathering behavior, and configuring default statistics collection parameters. This comprehensive statistics management package is central to maintaining accurate optimizer statistics.
Statistics preferences control how statistics are gathered including estimation percentage, degree of parallelism, histogram generation methods, granularity for partitioned objects, and many other options. Setting preferences at global, schema, or table level provides flexible control over statistics collection behavior, allowing customization where needed while maintaining consistent defaults.
The SET_GLOBAL_PREFS procedure sets database-wide default preferences affecting all statistics gathering unless overridden at more specific levels. SET_TABLE_PREFS sets preferences for individual tables, overriding global defaults for specific objects. GET_PREFS retrieves current preference settings, and DELETE_PREFS removes preferences, reverting to defaults.
Common preferences include ESTIMATE_PERCENT controlling sampling rates, METHOD_OPT defining histogram generation behavior, DEGREE specifying parallelism for statistics gathering, GRANULARITY controlling partition-level statistics for partitioned objects, and CASCADE determining whether index statistics are gathered with table statistics. These preferences significantly affect statistics quality and gathering performance.
Option B is incorrect because DBMS_OPTIMIZER is not a standard Oracle package for statistics management. Option C is incorrect because DBMS_STATISTICS is not the correct package name; Oracle uses DBMS_STATS. Option D is incorrect because DBMS_STAT_FUNCS is not a valid Oracle package name for statistics management.
Question 175:
What is the purpose of the SCOPE clause in ALTER SYSTEM commands?
A) To limit command scope to specific sessions
B) To control whether parameter changes affect memory, spfile, or both
C) To scope commands to specific tablespaces
D) To define command execution scope
Answer: B
Explanation:
The SCOPE clause in ALTER SYSTEM commands controls whether parameter changes affect memory, spfile, or both, providing precise control over when and how parameter modifications take effect. This capability is essential for managing dynamic parameter changes, ensuring parameter persistence across restarts, and coordinating parameter updates with maintenance operations.
SCOPE values include MEMORY to change only the current running instance parameter value without affecting the spfile, making the change effective immediately but lost after restart, SPFILE to modify only the server parameter file without affecting the currently running instance, making the change effective only after the next restart, and BOTH to update both the running instance and spfile, making the change immediate and persistent.
The appropriate SCOPE depends on the parameter and situation. For static parameters that cannot be changed while the instance runs, SCOPE=SPFILE is the only option, requiring restart to take effect. For dynamic parameters needing immediate effect that should persist, SCOPE=BOTH is appropriate. For testing parameter changes temporarily, SCOPE=MEMORY allows experimentation without permanent changes.
Examples include ALTER SYSTEM SET sga_target=4G SCOPE=BOTH to immediately change SGA target and persist the change, ALTER SYSTEM SET processes=500 SCOPE=SPFILE because processes is static and requires restart, and ALTER SYSTEM SET optimizer_mode=ALL_ROWS SCOPE=MEMORY to temporarily change optimizer mode for testing.
Option A is incorrect because limiting to specific sessions is not the purpose of SCOPE; session-level changes use ALTER SESSION. Option C is incorrect because SCOPE does not relate to tablespaces. Option D is incorrect because SCOPE specifically controls parameter change persistence, not general command execution scope.
Question 176:
Which view provides information about currently running RMAN backup and restore operations?
A) V$BACKUP_PROCESS
B) V$RMAN_STATUS
C) V$SESSION_LONGOPS
D) DBA_RMAN_OPERATIONS
Answer: C
Explanation:
The V$SESSION_LONGOPS view provides information about currently running RMAN backup and restore operations along with other long-running database operations, showing progress, estimated completion time, and resource usage. This view is essential for monitoring long-running operations including RMAN jobs, enabling administrators to track progress and estimate when operations will complete.
RMAN operations appear in V$SESSION_LONGOPS with rows showing the operation description, target object, start time, elapsed time, work completed, total work estimated, and estimated time remaining. For backup operations, this includes which files are being backed up, how much data has been processed, and how much remains. This visibility helps manage backup windows and diagnose slow backups.
The view updates periodically as operations progress, providing near real-time visibility into long-running activity. Each update refreshes elapsed time, completed work, and time remaining estimates, allowing monitoring of operation progress without querying RMAN directly. This is particularly useful for operations running in background sessions or spawned by scheduler jobs.
Additional columns provide context including the session identifier enabling correlation with V$SESSION for user information, SQL address and hash value for identifying the SQL statement, and message text describing the operation. This comprehensive information supports both casual monitoring and detailed performance analysis of long-running operations.
Option A is incorrect because VBACKUPPROCESSisnotastandardOracleview.OptionBispartiallyrelevantasVBACKUP_PROCESS is not a standard Oracle view. Option B is partially relevant as V BACKUPPROCESSisnotastandardOracleview.OptionBispartiallyrelevantasVRMAN_STATUS shows RMAN operation history but does not focus on current progress like V$SESSION_LONGOPS. Option D is incorrect because DBA_RMAN_OPERATIONS is not a standard view name.
Question 177:
What is the purpose of the COMPRESS FOR clause when creating or altering tables?
A) To compress all table data
B) To specify the compression method and optimization target like OLTP or query
C) To compress only specific columns
D) To enable encryption with compression
Answer: B
Explanation:
The COMPRESS FOR clause when creating or altering tables specifies the compression method and optimization target, allowing administrators to choose compression techniques optimized for different workload types like OLTP or data warehouse queries. This flexibility enables balancing compression ratio, CPU overhead, and access performance based on specific table usage patterns.
Compression options include COMPRESS FOR OLTP which uses advanced row compression optimized for transactional workloads with ongoing DML operations, COMPRESS FOR QUERY LOW and COMPRESS FOR QUERY HIGH which use columnar compression optimized for query-intensive workloads with varying compression ratios, and COMPRESS FOR ARCHIVE LOW and COMPRESS FOR ARCHIVE HIGH for maximum compression of historical data with minimal access requirements.
Each compression type makes different trade-offs between compression ratio, compression overhead, decompression overhead, and suitability for DML operations. OLTP compression provides moderate compression with low overhead for updates, making it suitable for active transactional tables. Query and archive compression provide higher compression ratios but are better suited for read-mostly or archival data.
The syntax includes CREATE TABLE table_name (…) COMPRESS FOR OLTP or ALTER TABLE table_name COMPRESS FOR QUERY HIGH. Compression can be enabled for entire tables, individual partitions in partitioned tables, or applied selectively to different data tiers based on access patterns and age.
Option A is incorrect because the clause does not simply compress all data but specifies how and for what workload type compression is applied. Option C is incorrect because column-level compression is not specified through COMPRESS FOR; this clause applies table-level or partition-level compression. Option D is incorrect because encryption is a separate feature from compression, though both can be enabled simultaneously.
Question 178:
Which parameter controls the maximum amount of time that undo data is retained for flashback queries?
A) UNDO_RETENTION
B) FLASHBACK_RETENTION
C) UNDO_RETENTION_GUARANTEE
D) Both A and C work together
Answer: D
Explanation:
Both UNDO_RETENTION and UNDO_RETENTION_GUARANTEE work together to control undo data retention for flashback queries. UNDO_RETENTION sets the target retention period in seconds, while UNDO_RETENTION_GUARANTEE determines whether Oracle must honor this retention period even if it means failing new transactions due to insufficient undo space.
UNDO_RETENTION specifies the minimum number of seconds that Oracle attempts to retain undo data after transactions commit. For example, UNDO_RETENTION=3600 indicates Oracle should try to keep undo for at least one hour. However, without guarantee, Oracle may overwrite undo data sooner if the undo tablespace becomes full and space is needed for new transactions.
UNDO_RETENTION_GUARANTEE enforces the retention period by preventing undo data from being overwritten until the retention period expires, even if this causes new transactions to fail due to insufficient undo space. When enabled, Oracle preserves undo data for the full retention period, ensuring flashback queries can reliably retrieve historical data within that window.
The interaction between these settings affects system behavior significantly. With UNDO_RETENTION set but UNDO_RETENTION_GUARANTEE disabled, retention is best-effort, and long-running queries may encounter “snapshot too old” errors if undo data is overwritten. With guarantee enabled, flashback queries succeed reliably within the retention window, but the database may experience errors for new transactions if undo space is exhausted.
Option A is partially correct as UNDO_RETENTION is key but does not guarantee retention alone. Option B is incorrect because FLASHBACK_RETENTION is not a valid Oracle parameter name. Option C is partially correct as UNDO_RETENTION_GUARANTEE is relevant but meaningless without UNDO_RETENTION setting the period. Option D correctly identifies that both parameters work together.
Question 179:
What is the purpose of the BITMAP JOIN INDEX in Oracle Database?
A) To create bitmap indexes on join results
B) To create an index on one table based on columns from another table that is frequently joined
C) To join bitmap indexes automatically
D) To improve join performance through special indexing
Answer: B
Explanation:
A bitmap join index creates an index on one table based on columns from another table that is frequently joined, storing the join result in the index structure to eliminate the need for join operations during query execution. This specialized index type is particularly valuable in data warehouse environments where dimension tables are frequently joined to fact tables on foreign key relationships.
The index stores the join between two tables, typically a fact table and a dimension table, capturing the relationship in the index structure. When queries join these tables on the indexed relationship, Oracle can satisfy the query using only the bitmap join index without accessing either table, dramatically improving performance for queries that filter on dimension attributes while accessing fact table rows.
Creating a bitmap join index requires specifying the indexed column from the dimension table, the fact table being indexed, and the join condition. For example, CREATE BITMAP INDEX sales_product_idx ON sales(products.category) FROM sales, products WHERE sales.product_id = products.product_id creates an index on sales that includes product category information from the products table.
Requirements include that tables must be joined on foreign key relationships, the fact table typically has many rows while the dimension table has relatively few, and queries must frequently filter on dimension attributes while selecting fact table data. These characteristics make bitmap join indexes ideal for star schema data warehouse designs.
Option A is incorrect because the index is not simply on join results but is a persistent index structure on one table incorporating information from another. Option C is incorrect because the index does not join existing bitmap indexes but creates a new index based on a join relationship. Option D is partially correct about improving join performance but does not precisely describe the mechanism of indexing one table using another table’s columns.
Question 180:
Which command is used to manually refresh a materialized view?
A) REFRESH MATERIALIZED VIEW view_name
B) EXEC DBMS_MVIEW.REFRESH(‘view_name’)
C) ALTER MATERIALIZED VIEW view_name REFRESH
D) UPDATE MATERIALIZED VIEW view_name
Answer: B
Explanation:
The EXEC DBMS_MVIEW.REFRESH(‘view_name’) command manually refreshes a materialized view by executing the refresh procedure from the DBMS_MVIEW package. This programmatic approach provides flexibility through various refresh options including refresh method, parallelism, and atomic refresh behavior, making it the standard way to manually control materialized view refresh operations.
The DBMS_MVIEW.REFRESH procedure accepts parameters controlling refresh behavior including the list of materialized views to refresh, method specifying C for complete refresh or F for fast refresh, atomic indicating whether the refresh should be atomic, and parallelism controlling parallel execution. For example, DBMS_MVIEW.REFRESH(‘MV_SALES_SUMMARY’,’C’) performs a complete refresh of the specified view.
Manual refresh is necessary when materialized views are created with REFRESH ON DEMAND rather than ON COMMIT, giving administrators explicit control over when refresh occurs. This approach is appropriate for large materialized views where refresh takes significant time and should occur during scheduled maintenance windows rather than automatically after each commit.
Alternative approaches include using DBMS_REFRESH package for managing refresh groups containing multiple materialized views that should refresh together, using scheduler jobs to automate periodic refresh operations, and for simple cases, using the REFRESH clause in SQL Developer or Enterprise Manager interfaces that internally call DBMS_MVIEW procedures.
Option A is incorrect because REFRESH MATERIALIZED VIEW is not valid SQL syntax in Oracle. Option C is incorrect because ALTER MATERIALIZED VIEW does not have a REFRESH clause for triggering refresh. Option D is incorrect because UPDATE is for DML operations on base tables, not for refreshing materialized views.
