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Question 121:
What is the purpose of the APPEND hint in SQL statements?
A) To add data to the end of tables only
B) To perform direct-path inserts bypassing the buffer cache and undo generation
C) To append execution plan details to output
D) To concatenate multiple INSERT statements
Answer: B
Explanation:
The APPEND hint in SQL statements performs direct-path inserts bypassing the buffer cache and undo generation, which significantly improves performance for bulk data loading operations. Direct-path inserts write data directly to datafiles above the high water mark of the table, avoiding the overhead of buffer cache management, undo generation for rollback, and redo generation for before-images.
When you use the APPEND hint in an INSERT statement like INSERT /*+ APPEND */ INTO target_table SELECT * FROM source_table, Oracle switches to direct-path mode. Data is formatted into blocks and written directly to new extents beyond the table’s high water mark. This approach is much faster than conventional inserts for large data volumes because it minimizes the overhead associated with normal DML operations.
Direct-path inserts have specific characteristics and limitations. They acquire exclusive locks on the table preventing concurrent DML from other sessions. Existing indexes are maintained but in a more efficient batch mode. Triggers do not fire for direct-path inserts. The operation commits automatically at completion, so you cannot roll back direct-path inserts. These characteristics make direct-path inserts suitable for data loading scenarios but not for normal transactional operations.
Parallel direct-path inserts can further improve performance by using multiple processes to write data concurrently. Combining the APPEND hint with the PARALLEL hint like INSERT /*+ APPEND PARALLEL(4) */ enables parallel direct-path insertion. This combination provides the fastest possible data loading method in Oracle for moving large volumes of data between tables.
Option A is incorrect because APPEND does not restrict where data is added within tables; it refers to appending blocks above the high water mark using direct-path operations. Option C is incorrect because the APPEND hint does not affect execution plan output or display. Option D is incorrect because APPEND does not concatenate multiple statements but rather changes how a single INSERT operates.
Question 122:
Which parameter controls whether Oracle automatically manages undo retention for flashback queries?
A) UNDO_RETENTION
B) UNDO_MANAGEMENT
C) AUTO_UNDO_RETENTION
D) UNDO_RETENTION is always automatic
Answer: A
Explanation:
The UNDO_RETENTION parameter controls how long Oracle retains undo data after transactions commit, which directly affects how far back flashback queries can retrieve historical data. While undo retention is influenced by this parameter, Oracle can automatically tune the actual retention based on undo tablespace size and system activity when the undo tablespace is configured with autoextend enabled and sufficient space is available.
UNDO_RETENTION specifies the minimum number of seconds that Oracle attempts to retain undo data after transactions commit. For example, UNDO_RETENTION=900 tells Oracle to try to keep undo information for at least 15 minutes after commit. This retention period determines how far back flashback queries like SELECT … AS OF TIMESTAMP can retrieve historical data and affects other flashback features.
Automatic undo retention tuning occurs when the undo tablespace has autoextend enabled and adequate space exists. In this configuration, Oracle may retain undo data longer than UNDO_RETENTION specifies if space permits. This automatic extension of retention helps prevent “snapshot too old” errors in long-running queries while still using UNDO_RETENTION as the baseline minimum.
The relationship between undo retention, undo tablespace size, and transaction volume determines actual retention. Heavy transaction workloads generating large amounts of undo data may cause Oracle to overwrite undo data sooner than UNDO_RETENTION specifies if the undo tablespace is too small. Properly sizing the undo tablespace relative to transaction volume and desired retention period is essential for reliable flashback capabilities.
Option B is incorrect because UNDO_MANAGEMENT controls whether automatic or manual undo management is used, not the retention period for undo data. Option C is incorrect because AUTO_UNDO_RETENTION is not a valid Oracle parameter name. Option D is incorrect because UNDO_RETENTION requires explicit configuration; retention is not purely automatic without this parameter setting.
Question 123:
What is the purpose of the DBA_TAB_MODIFICATIONS view?
A) To show audit records of table modifications
B) To display statistics about DML operations performed on tables since the last statistics gathering
C) To list table structure modifications
D) To show active modifications in progress
Answer: B
Explanation:
The DBA_TAB_MODIFICATIONS view displays statistics about DML operations performed on tables since the last statistics gathering, tracking the approximate number of inserts, updates, and deletes. This information helps Oracle’s automatic statistics gathering identify which tables have changed significantly and need updated statistics, and helps administrators understand data modification patterns.
Oracle maintains modification tracking internally as DML operations occur against tables. The tracked information includes approximate counts of inserts, updates, and deletes since statistics were last gathered for each table. These counts are not exact real-time values but are periodically flushed from memory to the data dictionary, typically every three hours or when thresholds are met.
The view contains columns showing the table owner and name, partition information for partitioned tables, the number of inserts, updates, and deletes, and timestamps indicating when modifications were last tracked and when statistics were last gathered. This data helps determine whether tables have become stale and need statistics updates to maintain optimizer effectiveness.
Automatic statistics gathering jobs query this view to prioritize which tables need statistics updates. Tables with modification counts exceeding certain thresholds relative to their total row count are considered stale and scheduled for statistics gathering. The default threshold is typically 10 percent of rows modified for tables with more than a certain number of rows.
Option A is incorrect because audit records are stored in audit trail tables and views, not in DBA_TAB_MODIFICATIONS which tracks statistics-related modification counts. Option C is incorrect because table structure modifications like adding columns are tracked in data dictionary base tables and timestamp columns in views like DBA_TABLES, not in DBA_TAB_MODIFICATIONS. Option D is incorrect because the view shows cumulative modification counts, not currently executing modifications.
Question 124:
Which command is used to rebuild an index online without blocking DML operations?
A) ALTER INDEX index_name REBUILD
B) ALTER INDEX index_name REBUILD ONLINE
C) CREATE INDEX index_name ONLINE
D) REBUILD INDEX index_name ONLINE
Answer: B
Explanation:
The ALTER INDEX index_name REBUILD ONLINE command rebuilds an index online without blocking DML operations, allowing applications to continue inserting, updating, and deleting data while the index is being rebuilt. This capability is essential for maintaining index performance through reorganization without requiring application downtime or maintenance windows.
Online index rebuild works by creating a new index structure while allowing DML to continue against the table. As the rebuild progresses, Oracle captures changes occurring during the rebuild in a journal table. When the initial rebuild completes, Oracle applies the journaled changes to the new index structure, then performs a quick lock to swap the old and new indexes. This brief lock is typically a few seconds regardless of index size.
Use cases for online index rebuild include reorganizing fragmented indexes to improve space efficiency and performance, moving indexes to different tablespaces, changing storage parameters, converting index types, and general index maintenance without impacting application availability. Regular index rebuilds may be necessary for indexes subject to heavy DML activity that causes fragmentation.
The ONLINE keyword is critical for avoiding locks. Without ONLINE, ALTER INDEX index_name REBUILD acquires exclusive locks preventing all DML on the table during the rebuild. For large indexes, this could mean hours of downtime. The ONLINE option incurs slightly more overhead during the rebuild due to change journaling but preserves application availability.
Option A is incorrect because ALTER INDEX REBUILD without the ONLINE keyword locks the table during rebuild, preventing DML operations. Option C is incorrect because CREATE INDEX is for creating new indexes, not rebuilding existing ones, though CREATE INDEX can include ONLINE for online index creation. Option D is incorrect because REBUILD INDEX is not valid syntax; the correct command is ALTER INDEX.
Question 125:
What is the purpose of the V$DATAFILE_HEADER view?
A) To show datafile names and locations
B) To display control file header information for each datafile including checkpoint and recovery information
C) To monitor datafile I/O statistics
D) To show datafile size and usage
Answer: B
Explanation:
The V$DATAFILE_HEADER view displays control file header information for each datafile including checkpoint and recovery information such as the checkpoint change number, creation time, and status. This view reads information directly from datafile headers rather than from the control file, making it valuable for diagnosing discrepancies between datafile headers and control file information.
Each datafile maintains a header containing metadata about the file including when it was created, which tablespace it belongs to, its checkpoint information indicating the last time it was synchronized with the control file, and its status indicating whether it is online or offline. V$DATAFILE_HEADER exposes this header information for administrative analysis and troubleshooting.
Common uses include verifying checkpoint SCNs to ensure datafiles are synchronized with the control file, identifying datafiles requiring recovery by comparing their checkpoint information with the database checkpoint, diagnosing media recovery situations where datafile headers may be inconsistent with control files, and investigating datafile status issues during startup.
Question 126:
Which clause in SELECT statements limits the number of rows returned starting from Oracle Database 12c?
A) LIMIT
B) TOP
C) FETCH FIRST
D) ROWCOUNT
Answer: C
Explanation:
The FETCH FIRST clause in SELECT statements limits the number of rows returned starting from Oracle Database 12c, providing standard SQL syntax for row limiting that is more intuitive than using ROWNUM. This clause appears at the end of SELECT statements after ORDER BY and provides a cleaner way to implement top-N queries and pagination.
The syntax includes multiple options for row limiting. FETCH FIRST n ROWS ONLY returns exactly n rows. FETCH FIRST n PERCENT ROWS ONLY returns n percent of the result set. The ONLY keyword can be replaced with WITH TIES to include additional rows that have the same values as the last row in the limited result set. For example, SELECT * FROM employees ORDER BY salary DESC FETCH FIRST 10 ROWS ONLY returns the 10 highest-paid employees.
Pagination support includes OFFSET for skipping rows before fetching. The syntax SELECT * FROM employees ORDER BY employee_id OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY skips the first 20 rows and returns the next 10, implementing pagination for rows 21 through 30. This approach is cleaner than nested ROWNUM queries used in earlier Oracle versions.
The FETCH FIRST clause works in conjunction with ORDER BY to ensure consistent results. Without ORDER BY, the rows returned are arbitrary and may vary between executions. When implementing top-N queries or pagination, always include ORDER BY to guarantee deterministic row selection and ordering.
Option A is incorrect because LIMIT is not Oracle syntax, though it exists in databases like MySQL and PostgreSQL. Option B is incorrect because TOP is SQL Server syntax, not Oracle. Option D is incorrect because ROWCOUNT is not a standard SQL clause for limiting rows, though it is a session setting in some databases.
Question 127:
What is the purpose of the ANALYZE command in Oracle Database?
A) To analyze SQL performance
B) To gather or delete statistics on tables and indexes
C) To analyze execution plans
D) To check database structure integrity
Answer: B
Explanation:
The ANALYZE command gathers or deletes statistics on tables and indexes, providing an older method for collecting optimizer statistics before the DBMS_STATS package became the recommended approach. While ANALYZE still functions in current Oracle versions, Oracle recommends using DBMS_STATS for statistics gathering due to its enhanced capabilities and better integration with automatic statistics management.
ANALYZE supports multiple operations including COMPUTE STATISTICS to calculate exact statistics by scanning every row, ESTIMATE STATISTICS to sample a percentage of rows for faster statistics gathering, DELETE STATISTICS to remove previously gathered statistics, and VALIDATE STRUCTURE to check for corruption in tables or indexes. The syntax includes ANALYZE TABLE table_name COMPUTE STATISTICS or ANALYZE INDEX index_name VALIDATE STRUCTURE.
Historical context helps understand ANALYZE. In older Oracle versions before the cost-based optimizer matured, ANALYZE was the primary method for gathering statistics. The rule-based optimizer did not use statistics, so ANALYZE was less important. As Oracle transitioned fully to the cost-based optimizer, statistics became critical, and ANALYZE was the original tool for gathering them.
Modern alternatives through DBMS_STATS provide better functionality including more sophisticated sampling methods, parallel statistics gathering for faster collection on large objects, better histogram generation for skewed data, automatic statistics management integration, and statistics history for restoring previous statistics if new ones cause problems. These advantages make DBMS_STATS preferable to ANALYZE.
Option A is incorrect because analyzing SQL performance involves execution plan analysis and performance views, not the ANALYZE command which focuses on object statistics. Option C is incorrect because execution plan analysis uses EXPLAIN PLAN and related tools, not ANALYZE. Option D is incorrect because checking database structure integrity uses DBMS_REPAIR and other validation tools, though ANALYZE with VALIDATE STRUCTURE checks object-level integrity.
Question 128:
Which parameter specifies the maximum number of open cursors per session?
A) MAX_CURSORS
B) OPEN_CURSORS
C) CURSOR_LIMIT
D) SESSION_CURSORS
Answer: B
Explanation:
The OPEN_CURSORS parameter specifies the maximum number of open cursors that a session can have simultaneously, controlling resource consumption related to cursor management and preventing individual sessions from exhausting system resources through excessive cursor usage. When a session attempts to open more cursors than this limit allows, it receives an error indicating maximum open cursors exceeded.
Cursors are memory structures that Oracle uses to process SQL statements. Each time an application executes a SQL statement, Oracle allocates a cursor to manage the statement’s execution. Properly written applications close cursors when finished with them, but poorly written applications may leak cursors by failing to close them, eventually hitting the OPEN_CURSORS limit.
The default value for OPEN_CURSORS is typically 50, which is sufficient for many simple applications but may be too low for complex applications that manage many concurrent SQL operations. Applications using connection pooling, frameworks with extensive cursor usage, or those executing many different SQL statements concurrently may require higher values. Common production settings range from 300 to 1000 depending on application requirements.
Option A is incorrect because MAX_CURSORS is not a valid Oracle parameter name, though it conceptually describes the purpose of OPEN_CURSORS. Option C is incorrect because CURSOR_LIMIT is not an Oracle parameter. Option D is incorrect because SESSION_CURSORS is not the parameter that limits open cursors, though it relates to cursor management in other ways.
Question 129:
What is the purpose of the DBMS_METADATA package?
A) To extract DDL statements for database objects
B) To manage database file metadata
C) To store application metadata
D) To compress metadata storage
Answer: A
Explanation:
The DBMS_METADATA package extracts DDL statements for database objects, providing programmatic access to the data dictionary to generate CREATE statements for tables, indexes, users, and other database objects. This capability is essential for documenting database schemas, migrating objects between environments, and generating scripts for object recreation.
The package provides multiple procedures and functions for metadata extraction. GET_DDL retrieves DDL for a single object, accepting object type and name as parameters. GET_DEPENDENT_DDL retrieves DDL for dependent objects like indexes or constraints for a specified table. OPEN, SET_FILTER, FETCH_CLOB, and CLOSE provide a more flexible API for extracting metadata for multiple objects matching specific criteria.
Common usage involves extracting table definitions for documentation or migration. For example, SELECT DBMS_METADATA.GET_DDL(‘TABLE’, ‘EMPLOYEES’, ‘HR’) returns the complete CREATE TABLE statement for the EMPLOYEES table in the HR schema. The generated DDL includes all table attributes, storage clauses, and constraints, providing a complete definition.
Customization options control DDL output format through SET_TRANSFORM_PARAM procedure. Options include whether to include storage clauses, whether to generate SEGMENT CREATION IMMEDIATE or DEFERRED clauses, tablespace specifications, and various formatting options. These transformations allow generating DDL suitable for different target environments or documentation purposes.
Export utilities like Data Pump use DBMS_METADATA internally to extract object definitions. Understanding DBMS_METADATA helps administrators work more effectively with metadata extraction and customize DDL generation for specific needs beyond what export tools provide by default.
Option B is incorrect because managing database file metadata involves data dictionary views and file system operations, not the DBMS_METADATA package which focuses on object definition extraction. Option C is incorrect because storing application metadata is an application design concern, not the purpose of DBMS_METADATA which reads rather than stores metadata. Option D is incorrect because metadata compression is not a function of DBMS_METADATA.
Question 130:
Which view shows information about database instance parameters that can be modified with ALTER SYSTEM?
A) V$PARAMETER
B) V$SYSTEM_PARAMETER
C) DBA_PARAMETERS
D) V$SPPARAMETER
Answer: A
Explanation:
The V$PARAMETER view shows information about database instance parameters including whether they can be modified with ALTER SYSTEM, their current values, default values, and whether they are modifiable at the session or system level. This view is essential for understanding instance configuration, determining which parameters can be changed dynamically, and monitoring current parameter settings.
Each row in V$PARAMETER represents one initialization parameter with columns including NAME for the parameter name, VALUE for its current setting, ISDEFAULT indicating whether it uses the default value, ISMODIFIED showing whether it has been changed from default, and ISSYS_MODIFIABLE indicating whether and how it can be changed with ALTER SYSTEM. The ISSYS_MODIFIABLE column values include IMMEDIATE for parameters that can be changed and take effect immediately, DEFERRED for parameters that take effect for subsequent sessions, and FALSE for static parameters requiring instance restart.
Querying this view helps administrators identify which parameters can be tuned without downtime. For example, SELECT name, value, issys_modifiable FROM v$parameter WHERE name LIKE ‘%target%’ shows memory target parameters and indicates whether they can be changed dynamically. This information guides tuning efforts and maintenance planning.
Question 131:
What is the purpose of the WHENEVER SQLERROR command in SQL*Plus?
A) To handle SQL syntax errors
B) To define actions to take when SQL statements return errors during script execution
C) To suppress error messages
D) To debug SQL statements
Answer: B
Explanation:
The WHENEVER SQLERROR command in SQLPlus defines actions to take when SQL statements return errors during script execution, providing error handling capabilities in SQLPlus scripts. This command allows scripts to exit upon errors, continue processing, or execute operating system commands based on error conditions, making scripts more robust and enabling automated error response.
The syntax includes WHENEVER SQLERROR followed by an action. Common actions include EXIT which terminates SQLPlus when an error occurs, CONTINUE which ignores errors and continues script execution, and operating system commands that execute when errors occur. For example, WHENEVER SQLERROR EXIT SQL.SQLCODE causes SQLPlus to exit with the error code when any SQL error occurs.
Use cases include production deployment scripts that must abort if any statement fails, preventing partial deployments that could leave databases in inconsistent states. Scripts that must complete even if some statements fail use CONTINUE to keep processing. Automated scripts might use WHENEVER SQLERROR to send notifications or log errors to external systems.
Additional options control which errors trigger the action. WHENEVER SQLERROR EXIT FAILURE exits on any error, WHENEVER SQLERROR EXIT WARNING exits on warnings, and WHENEVER SQLERROR EXIT SQL.SQLCODE exits with the specific Oracle error code. These options provide granular control over error handling behavior.
Option A is incorrect because WHENEVER SQLERROR does not handle syntax errors in the sense of correcting them but rather defines response actions when errors occur. Option C is incorrect because while you can use CONTINUE to make scripts proceed despite errors, suppressing messages requires SET commands, not WHENEVER SQLERROR. Option D is incorrect because debugging involves different tools and approaches; WHENEVER SQLERROR handles error responses in scripts.
Question 132:
Which parameter controls the maximum number of archived redo log files that can be created per destination?
A) MAXLOGFILES
B) LOG_ARCHIVE_MAX_PROCESSES
C) There is no limit parameter; it depends on file system space
D) ARCHIVE_LOG_MAX
Answer: C
Explanation:
There is no specific parameter that limits the maximum number of archived redo log files that can be created per destination; the number is limited only by available file system space and operating system file count limitations. Oracle will continue archiving online redo log files as long as space is available in the archive destination, making space management critical for archive log destinations.
Archive log destinations must be monitored to ensure sufficient space exists for continued archiving. If an archive destination fills up and Oracle cannot write archived logs, the database may hang until space is freed because Oracle must preserve all redo information to maintain recoverability. This situation can cause production outages if not addressed promptly.
Space management strategies include configuring the Fast Recovery Area which provides automatic space management for archived logs, setting up multiple archive destinations with one marked as optional, implementing RMAN retention policies that automatically delete obsolete archived logs, monitoring archive destination space usage through alerts, and establishing procedures for quickly freeing space when needed.
The relationship between archiving and database operation is critical. When running in ARCHIVELOG mode, Oracle must successfully archive each online redo log before it can be reused. If archiving fails due to space constraints, log file I/O errors, or other issues, the log writer eventually runs out of available redo logs and the database halts new transactions until archiving resumes.
Option A is incorrect because MAXLOGFILES limits the number of redo log groups that can be defined in the control file, not the number of archived log files. Option B is incorrect because LOG_ARCHIVE_MAX_PROCESSES controls the number of ARCn processes for archiving, not the number of archived files. Option D is incorrect because ARCHIVE_LOG_MAX is not a valid Oracle parameter name.
Question 133:
What is the purpose of transportable tablespaces in Oracle Database?
A) To compress tablespace data for transport
B) To move or copy tablespaces between databases with minimal data copying
C) To backup tablespaces to tape
D) To encrypt tablespace during transport
Answer: B
Explanation:
Transportable tablespaces move or copy tablespaces between databases with minimal data copying by transporting the datafiles themselves along with metadata rather than extracting and reloading all data. This feature dramatically reduces the time required to move large amounts of data between databases compared to traditional export and import operations.
The transport process involves making tablespaces read-only, using Data Pump to export only metadata about objects in the tablespaces, copying the datafiles to the target system, importing the metadata into the target database using Data Pump, and making tablespaces read-write in the target database. Because datafiles are copied rather than data being extracted row-by-row, the operation completes much faster for large tablespaces.
Use cases include migrating data between databases for upgrades, consolidating data from multiple databases into a data warehouse, moving historical data to archive databases, and creating test or development environments with production data. For databases measured in terabytes, transportable tablespaces can reduce migration time from days to hours.
Requirements and restrictions apply to transportable tablespaces. Source and target databases must have the same block size for transported tablespaces, character sets must be compatible, endian formats must match or conversion must be performed, and the target database must not already contain objects with the same names as those being transported. These requirements must be verified before beginning transport operations.
Option A is incorrect because compression is a separate feature from transportability, though compressed tablespaces can be transported. Option C is incorrect because backup to tape uses RMAN and backup utilities, not tablespace transport features. Option D is incorrect because encryption is a separate feature from transport, though encrypted tablespaces can be transported if encryption keys are properly managed.
Question 134:
Which view provides information about SQL profiles created by SQL Tuning Advisor?
A) DBA_SQL_PROFILES
B) V$SQL_PROFILE
C) DBA_ADVISOR_PROFILES
D) USER_SQL_PROFILES
Answer: A
Explanation:
The DBA_SQL_PROFILES view provides information about SQL profiles created by SQL Tuning Advisor including the profile name, category, SQL text signature, status, and creation date. SQL profiles provide additional information to the optimizer to help it make better execution plan choices without modifying SQL statements, making them a key feature of Oracle’s automatic SQL tuning capabilities.
SQL profiles differ from SQL plan baselines in their approach to performance management. Profiles provide supplemental statistics and information to guide the optimizer toward better plans while still allowing the optimizer to adapt to changing conditions. Baselines fix specific execution plans to prevent plan regression. Profiles are generally more flexible but provide less control than baselines.
The DBA_SQL_PROFILES view includes columns showing the profile name which uniquely identifies each profile, the category used to organize profiles with DEFAULT being the standard category, the signature identifying the SQL statement this profile applies to, status indicating whether the profile is ENABLED or DISABLED, and timestamps showing when the profile was created and last modified.
Managing SQL profiles involves accepting recommendations from SQL Tuning Advisor which creates profiles automatically, manually enabling or disabling profiles through DBMS_SQLTUNE procedures, dropping profiles that no longer provide value or cause problems, and monitoring profile effectiveness through comparison queries examining execution plans and performance metrics before and after profile application.
Option B is incorrect because V$SQL_PROFILE is not a standard Oracle dynamic performance view for SQL profile information. Option C is incorrect because DBA_ADVISOR_PROFILES is not the correct view name; advisor information is tracked separately from SQL profiles. Option D is incorrect because USER_SQL_PROFILES would show only profiles owned by the current user, and SQL profiles are system-level objects visible through DBA_SQL_PROFILES.
Question 135:
What is the purpose of the PARALLEL hint in SQL statements?
A) To create multiple copies of result data
B) To enable parallel execution of a SQL statement using multiple server processes
C) To run multiple statements simultaneously
D) To parallelize application logic
Answer: B
Explanation:
The PARALLEL hint in SQL statements enables parallel execution of a SQL statement using multiple server processes, allowing Oracle to divide work among multiple processes that execute concurrently. This capability can dramatically reduce execution time for data-intensive operations like full table scans, large sorts, and complex joins by leveraging multiple CPUs and I/O channels.
Parallel execution divides operations into smaller pieces called granules that are processed independently by parallel execution servers. For a full table scan, Oracle divides the table into ranges of blocks with each parallel server scanning its assigned range. Results are combined by a coordinator process that manages the parallel execution and returns final results to the client.
The syntax includes specifying the degree of parallelism. SELECT /*+ PARALLEL(employees 4) */ * FROM employees causes Oracle to use four parallel servers to scan the employees table. The optimizer may adjust the degree based on system resources and workload, but the hint requests a specific parallelism level. PARALLEL without a degree allows Oracle to determine optimal parallelism automatically.
Parallel execution is most beneficial for large data volumes where the overhead of coordinating multiple processes is justified by the time savings from concurrent processing. Small tables or operations involving limited data may run slower with parallelism due to coordination overhead. Proper use requires understanding when parallelism helps versus when serial execution is more efficient.
Option A is incorrect because parallel execution does not create multiple copies of result data but processes data concurrently to produce a single result faster. Option C is incorrect because the PARALLEL hint affects a single statement’s execution, not running multiple statements simultaneously. Option D is incorrect because application logic parallelization is an application design concern, not what the PARALLEL hint accomplishes.
Question 136:
Which clause in CREATE TABLE automatically generates sequential numbers for a column starting from Oracle Database 12c?
A) AUTO_INCREMENT
B) IDENTITY
C) SEQUENCE
D) AUTO_GENERATE
Answer: B
Explanation:
The IDENTITY clause in CREATE TABLE automatically generates sequential numbers for a column starting from Oracle Database 12c, providing a simpler alternative to manually creating sequences and triggers for auto-numbering columns. Identity columns eliminate the need to explicitly call sequence.NEXTVAL in INSERT statements, making application code simpler and more portable across database systems.
The syntax includes the IDENTITY keyword in the column definition. For example, CREATE TABLE orders (order_id NUMBER GENERATED ALWAYS AS IDENTITY, order_date DATE, amount NUMBER) creates an order_id column that automatically receives sequential values. The GENERATED ALWAYS clause means values cannot be explicitly inserted; Oracle always generates them. GENERATED BY DEFAULT allows explicit values but generates them when not provided.
Identity column options control sequence behavior including START WITH to specify the starting value, INCREMENT BY to define the increment amount, MAXVALUE and MINVALUE to set upper and lower bounds, CACHE to determine how many values are preallocated in memory, and ORDER or NOORDER to control whether values are guaranteed to be generated in order. These options mirror sequence object options.
Oracle implements identity columns using implicit sequences created automatically when the table is created. The underlying sequence is visible in data dictionary views and can be queried for information, but it is managed automatically by Oracle. Dropping the table automatically drops the associated sequence, simplifying object management.
Option A is incorrect because AUTO_INCREMENT is MySQL syntax, not Oracle. Option C is incorrect because SEQUENCE is used to create sequence objects separately, not as a column clause for identity columns. Option D is incorrect because AUTO_GENERATE is not valid Oracle syntax for automatic number generation.
Question 137:
What is the purpose of the V$TRANSACTION view?
A) To show all transaction history
B) To display currently active transactions and their characteristics
C) To monitor transaction performance statistics
D) To show transaction rollback information
Answer: B
Explanation:
The V$TRANSACTION view displays currently active transactions and their characteristics including transaction start time, undo segment used, undo block consumption, and transaction status. This view is essential for monitoring active transaction activity, identifying long-running transactions, and diagnosing issues related to transaction processing and undo space consumption.
Each row in V$TRANSACTION represents one currently active transaction with columns showing the transaction address, undo segment number and name, undo blocks used, undo records generated, transaction start SCN and time, status, and space information. This detailed view helps administrators understand current transaction activity and resource consumption.
Common administrative tasks include identifying transactions consuming excessive undo space by querying for transactions with high undo block counts, finding long-running transactions by examining start times, correlating transactions with sessions by joining VTRANSACTIONwithVTRANSACTION with V TRANSACTIONwithVSESSION on the SADDR column, and monitoring transaction activity patterns during troubleshooting.
The relationship between transactions and sessions is exposed through joining VTRANSACTIONwithVTRANSACTION with V TRANSACTIONwithVSESSION. A session may have at most one active transaction at a time, but not all sessions have active transactions. Only sessions that have executed DML statements and not yet committed or rolled back appear in V$TRANSACTION.
Option A is incorrect because VTRANSACTIONshowsonlycurrentlyactivetransactions,nothistoricaltransactionswhichwouldrequireaudittrailsorarchivedredologanalysis.OptionCisincorrectbecausedetailedtransactionperformancestatisticscomefromotherviews;VTRANSACTION shows only currently active transactions, not historical transactions which would require audit trails or archived redo log analysis. Option C is incorrect because detailed transaction performance statistics come from other views; V TRANSACTIONshowsonlycurrentlyactivetransactions,nothistoricaltransactionswhichwouldrequireaudittrailsorarchivedredologanalysis.OptionCisincorrectbecausedetailedtransactionperformancestatisticscomefromotherviews;VTRANSACTION focuses on current transaction state and resource usage. Option D is incorrect because rollback information is stored in undo segments and is not primarily displayed through V$TRANSACTION.
Question 138:
Which parameter specifies the size of the Java pool in the SGA?
A) JAVA_POOL_SIZE
B) SGA_JAVA_SIZE
C) JAVA_MEMORY_SIZE
D) POOL_JAVA_SIZE
Answer: A
Explanation:
The JAVA_POOL_SIZE parameter specifies the size of the Java pool in the SGA, which stores Java class definitions, Java objects in session space, and shared Java data when Java is used within the database through Java stored procedures or JDBC internals. This pool is necessary when applications use Java in the database but can be set to zero if Java functionality is not used.
The Java pool supports Oracle’s integration of Java into the database environment including Java stored procedures written in Java and stored in the database, Oracle JVM executing Java code within database sessions, and Java-based Oracle features that use Java internally. The pool size should be adequate to cache frequently used Java classes and objects without causing excessive loading and garbage collection.
Sizing the Java pool depends on the extent of Java usage in the database. Applications with many Java stored procedures or extensive use of Java-based features like XML DB require larger Java pools. Minimal Java usage may require only the default size, while systems not using Java at all can set JAVA_POOL_SIZE to zero to conserve memory for other SGA components.
When automatic shared memory management is enabled through SGA_TARGET, Oracle can dynamically size the Java pool based on workload demands. Manual sizing through JAVA_POOL_SIZE is necessary when not using automatic management or when you want to establish minimum or maximum bounds for the Java pool regardless of automatic tuning.
Option B is incorrect because SGA_JAVA_SIZE is not a valid Oracle parameter name. Option C is incorrect because JAVA_MEMORY_SIZE is not the correct parameter name for the Java pool in the SGA. Option D is incorrect because POOL_JAVA_SIZE is not valid Oracle parameter naming convention.
Question 139:
What is the purpose of Oracle Database Resource Manager consumer groups?
A) To group users for security purposes
B) To categorize database sessions for resource allocation and limits
C) To manage consumer applications
D) To group database objects
Answer: B
Explanation:
Oracle Database Resource Manager consumer groups categorize database sessions for resource allocation and limits, enabling administrators to control how CPU time, I/O operations, parallel execution servers, and other resources are distributed among different types of workload. Consumer groups are fundamental to implementing resource management policies that ensure critical work receives adequate resources.
Sessions are assigned to consumer groups based on various criteria including username, service name, client program name, or explicit calls to DBMS_SESSION procedures. Once assigned to a group, sessions receive resources according to the active resource plan which defines resource allocation rules for each consumer group. This mechanism enables prioritizing critical applications over less important workloads.
Creating consumer groups involves using the DBMS_RESOURCE_MANAGER package to create groups with descriptive names like CRITICAL_APPS, BATCH_JOBS, or REPORTING. Each group represents a category of work with similar resource requirements or priorities. Resource plans then specify how resources should be divided among groups, such as giving CRITICAL_APPS 70 percent of CPU during contention.
Resource limits can be applied at the consumer group level including maximum degree of parallelism, maximum idle time before sessions are automatically terminated, maximum execution time limits for SQL statements, undo pool limits to control undo space consumption, and session pool limits controlling the number of concurrent sessions from a group. These limits prevent resource monopolization.
Option A is incorrect because grouping users for security uses roles and privileges, not consumer groups which focus on resource management. Option C is incorrect because consumer groups categorize database sessions, not external consumer applications. Option D is incorrect because grouping database objects involves schemas and tablespaces, not Resource Manager consumer groups.
Question 140:
Which view shows information about database jobs scheduled using the older DBMS_JOB package?
A) DBA_JOBS
B) DBA_SCHEDULER_JOBS
C) V$JOBS
D) USER_JOBS
Answer: A
Explanation:
The DBA_JOBS view shows information about database jobs scheduled using the older DBMS_JOB package including job number, what procedure or anonymous block to execute, when jobs last ran and will next run, and job status. While DBMS_JOB is deprecated in favor of DBMS_SCHEDULER, legacy systems may still use it, making DBA_JOBS relevant for managing older job implementations.
Job information in DBA_JOBS includes the job number uniquely identifying each job, the job procedure or SQL to execute, next run date showing when the job will execute next, interval expression determining the schedule, whether the job is currently running or broken, and the number of failures. This information helps administrators monitor and manage legacy job execution.
The distinction between DBA_JOBS and DBA_SCHEDULER_JOBS reflects Oracle’s evolution in job scheduling. DBA_JOBS shows jobs created with DBMS_JOB.SUBMIT and related procedures, while DBA_SCHEDULER_JOBS shows jobs created with DBMS_SCHEDULER.CREATE_JOB. These are separate scheduling systems, and jobs in one do not appear in views for the other.
Migration from DBMS_JOB to DBMS_SCHEDULER is recommended for systems still using the older package because DBMS_SCHEDULER provides better functionality including more flexible scheduling options, better logging and error handling, support for job chains and complex workflows, integration with Resource Manager for resource control, and overall better manageability. Migration typically involves recreating jobs using DBMS_SCHEDULER interfaces.
Option B is incorrect because DBA_SCHEDULER_JOBS shows jobs scheduled through DBMS_SCHEDULER, not the older DBMS_JOB package. Option C is incorrect because V$JOBS is not a standard Oracle dynamic performance view. Option D is partially correct for showing jobs owned by the current user but DBA_JOBS provides database-wide visibility.
