The Best Oracle 1Z0-084 Study Guides and Dumps of 2025
Top Oracle 1Z0-084 Exam Audio Study Guide! Practice Questions Edition
Oracle 1Z0-084 certification exam consists of 75 multiple-choice questions that must be answered in 120 minutes. 1Z0-084 exam is computer-based and can be taken at authorized testing centers worldwide. Candidates must score at least 63% to pass the exam and earn the certification. 1Z0-084 exam fee is $245 USD, and candidates can register for the exam on the Oracle website.
To obtain the Oracle 1Z0-084 certification, candidates must have a strong foundational understanding of Oracle Database 19c and be proficient in performance tuning and management techniques. 1Z0-084 exam consists of 70 multiple-choice questions and must be completed within 105 minutes. The passing score for the exam is 63% and candidates must also agree to the Oracle Certification Program policies before receiving their certification.
Oracle Database 19c Performance and Tuning Management exam aims to assess the candidates' knowledge of this important area of expertise. In particular, the exam focuses on the design and implementation of system infrastructure, the management of database performance and its optimization, the identification and resolution of performance issues in the database, and knowledge of performance monitoring and data management.
NEW QUESTION # 30
A database supporting a mixed workload is hosted on a server with 64 CPUs.
A large number of free buffer waits and buffer busy waits occur affecting performance.
The buffer cache size was then increased but after a few hours, the same wait events occur more often than before the change.
Examine these parameter settings:
Which two actions can help reduce the number of these waits7
- A. reducing the values of DB_FILE_MULTILOCK_READ_COUNT to 64
- B. increasing the value of DB_FILE_MULTIBLOCK_READ_COUNT to 128
- C. Increasing the size of MEMORYTARGET
- D. increasing the value of DBWRITERPROCESSES to 64,
- E. setting dbwr_io_slaves to 64
Answer: D,E
Explanation:
Given a server with 64 CPUs, if the buffer cache size increase did not alleviate free buffer waits and buffer busy waits, one can look into optimizing I/O and the efficiency of the DB writer processes.
C: Setting theDBWR_IO_SLAVESparameter to a non-zero value, such as the number of CPUs, would initiate I/O slave processes to assist the DB writer process. This can help reduce I/O contention when writing from the buffer cache to disk, particularly for systems without asynchronous I/O capabilities.
D: Increasing the value ofDBWRITERPROCESSESenables multiple DB writer processes to be active simultaneously. In a system with many CPUs, such as 64, increasing this value can improve the write throughput to disk and potentially reduce buffer busy waits.
References:
* Oracle Database Reference, 19c
* Oracle Database Performance Tuning Guide, 19c
NEW QUESTION # 31
A database instance is suffering poor I/O performance on two frequently accessed large tables.
No Big Table caching occurs in the database.
Examine these parameter settings:
Which are two actions either one of which will allow Big Table caching to occur?
- A. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 25
- B. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 50
- C. Setting PARALLEL_DEGREE_POLICYAUTO
- D. Setting DB_KEEP_CACHE_SIZE to at least 50M
- E. Setting PARALLEL_DEGREE_POLICYADAPTIVE
- F. Increasing DB_CACHESIZE to 1 G
Answer: A,F
Explanation:
Big Table caching is a feature that allows frequently accessed large tables to be cached in memory to improve I/O performance. From the parameter settings provided, Big Table caching is not occurring because DB_BIG_TABLE_CACHE_PERCENT_TARGETis set to 10, which is the minimum threshold for enabling the feature, but the size of the cache is too small for the big tables to be effectively cached.
To enable Big Table caching, one of the following actions could be taken:
* C (Correct):IncreasingDB_BIG_TABLE_CACHE_PERCENT_TARGETto at least 25. This action would allocate a larger percentage of the buffer cache for storing big tables, which could allow for caching large tables and thus improve I/O performance.
* D (Correct):IncreasingDB_CACHE_SIZEto 1G. Since the size of the buffer cache is a determining factor for how much data can be cached, increasing this parameter would provide more memory space for big tables to be cached.
Options A, B, E, and F will not enable Big Table caching because:
* A:IncreasingDB_BIG_TABLE_CACHE_PERCENT_TARGETto 50 without adjusting the overall size of the cache might still not be sufficient if theDB_CACHE_SIZEis not large enough to hold the big tables.
* B:SettingDB_KEEP_CACHE_SIZEto at least 50M only specifies a separate buffer pool for objects with the KEEP cache attribute and does not affect Big Table caching.
* E:andF:Changing thePARALLEL_DEGREE_POLICYtoADAPTIVEorAUTOinfluences the behavior of parallel execution but does not directly enable or influence Big Table caching.
References:
* Oracle Database Performance Tuning Guide:Big Table Caching
* Oracle Database Reference:DB_BIG_TABLE_CACHE_PERCENT_TARGET
* Oracle Database Reference:DB_CACHE_SIZE
NEW QUESTION # 32
Multiple sessions are inserting data concurrently into a table that has an LOB column.
At some point in time, one of the sessions cannot find available space in the LOB segment and needs to allocate a new extent.
Which wait event will be raised in the other sessions that need space in the LOB column?
- A. enq: TM - contention
- B. enq: HW - contention
- C. enq: TX - allocate ITL entry
- D. enq: SQ - contention
Answer: B
Explanation:
When sessions concurrently insert data into a table with an LOB column and one session needs to allocate a new extent because it cannot find available space, the wait event associated with this contention is "enq: HW - contention". The HW stands for High Water Mark which is related to space allocation in the database segment. When a session needs to allocate a new extent, it may raise this wait event in other sessions that are also attempting to allocate space in the same LOB segment.
References
* Oracle Database 19c Reference Guide - enq: HW - contention
NEW QUESTION # 33
Which statement is true about DB time in V$$YS_TIME_MODEL?
- A. DB time can be many times greater than the elapsed time since the database instance started.
- B. DB time includes the time spent executing the RMAN backup and restore command.
- C. DB tine excludes the time spent waiting for a CPU in the operating system run queue.
- D. DB time is organized as a simple list of statistics and any time period is attributable to only one statistic.
Answer: A
Explanation:
DB time includes the time spent on user and background processes. It can be greater than the elapsed time because it accumulates the active time of all the processes. For example, if two sessions are each active for 2 seconds at the same time, DB time would accumulate 4 seconds, while the elapsed time would be only 2 seconds.References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Reference, 19c
NEW QUESTION # 34
You must configure and enable Database Smart Flash Cache for a database.
You configure these flash devices:
Examine these parameter settings:
What must be configured so that the database uses these devices for the Database Smart Flash Cache?
- A. Set DB_FLASH_CACHE_SIZE to 256G and change device /dev/sdk to 128G.
- B. Set DB_FLASH_CACHE_SIZE to 192G and MEMORY_TARGET to 256G.
- C. Set DB_FLASH_CACHE_SIZE parameter to 128G, 64G.
- D. Set DB_FLASH_CACHE_SIZE parameter to 192G.
- E. Disable Automatic Memory Management and set SGA_TARGET to 256G.
Answer: C
Explanation:
To configure and enable Database Smart Flash Cache, you must set the DB_FLASH_CACHE_SIZE parameter to reflect the combined size of the flash devices youintend to use for the cache. In this scenario, two flash devices are configured: /dev/sdj with 128G and /dev/sdk with 64G.
* Determine the combined size of the flash devices intended for the Database Smart Flash Cache. In this case, it's 128G + 64G = 192G.
* However, Oracle documentation suggests setting DB_FLASH_CACHE_SIZE to the exact sizes of the individual devices, separated by a comma when multiple devices are used.
* Modify the parameter in the database initialization file (init.ora or spfile.ora) or using an ALTER SYSTEM command. Here's the command for altering the system setting:
ALTER SYSTEM SET DB_FLASH_CACHE_SIZE='128G,64G' SCOPE=SPFILE;
* Since this is a static parameter, a database restart is required for the changes to take effect.
* Upon database startup, it will allocate the Database Smart Flash Cache using the provided sizes for the specified devices.
It is important to note that MEMORY_TARGET and MEMORY_MAX_TARGET parameters should be configured independently of DB_FLASH_CACHE_SIZE. They control the Oracle memory management for the SGA and PGA, and do not directly correlate with the flash cache configuration.
References
* Oracle Database 19c Documentation on Database Smart Flash Cache
* Oracle Support Articles and Community Discussions on DB_FLASH_CACHE_SIZE Configuration
NEW QUESTION # 35
Which three statements are true about using the in Memory (IM) column store?
- A. It does not require all database data to fit in memory to improve query performance.
- B. It does not improve performance for queries using cached results of function evaluations on columns from the same table.
- C. It does not improve performance for queries that use join groups on columns from different tables.
- D. It can improve OLTP workload performance by avoiding the use of indexes.
- E. It improves performance for queries joining several tables using bloom filter joins.
- F. It does not improve performance for queries using user-defined virtual column results.
Answer: A,D,E
Explanation:
The Oracle In-Memory (IM) column store feature enhances the performance of databases by providing a fast columnar storage format for analytical workloads while also potentially benefiting OLTP workloads.
* C (True):It can improve OLTP workload performance by providing a faster access path for full table scans and reducing the need for indexes in certain scenarios, as the In-Memory store allows for efficient in-memory scans.
* E (True):The In-Memory column store does not require all database data to fit in memory. It can be used selectively for performance-critical tables or partitions, and Oracle Database will manage the population and eviction of data as needed.
* F (True):In-Memory column store can significantly improve performance for queries joining several tables, especially when bloom filters are used, as they are highly efficient with the columnar format for large scans and join processing.
The other options provided are not correct in the context of the In-Memory column store:
* A (False):While In-Memory column store is designed for analytical queries rather than caching results of function evaluations, it does not specifically avoid improving performance for queries using cached results of function evaluations.
* B (False):In-Memory column store can improve the performance of queries that use join groups, which can be used to optimize joins on columns from different tables.
* D (False):In-Memory column store can improve the performance of queries using expressions, including user-defined virtual columns, because it supports expression statistics which help in
* optimizing such queries.
References:
* Oracle Database In-Memory Guide:In-Memory Column Store in Oracle Database
* Oracle Database In-Memory Guide:In-Memory Joins
* Oracle Database In-Memory Guide:In-Memory Aggregation
NEW QUESTION # 36
Which Optimizer component helps decide whether to use a nested loop join or a hash join in an adaptive execution plan?
- A. Statistics Collector
- B. Dynamic Statistics
- C. Statistics Feedback
- D. Automatic Reoptimization
- E. SQL Plan Directives
Answer: A
Explanation:
In an adaptive execution plan, the Optimizer makes runtime decisions between nested loop and hash joins using a statistics collector. The collector is a row source that collects statistics about the rows it processes and can adapt the plan based on the number of rows processed.
References:
* Oracle Database SQL Tuning Guide, 19c
NEW QUESTION # 37
Examine this statement and output:
Which three statements are true?
- A. Session 9857 is not waiting.
- B. Session 8779 may be waiting due to a network problem.
- C. Both 9822 and 8779 sessions are waiting for operating system resources.
- D. Session 9857 waited 1354 seconds for another process, which was also waiting for a transaction to end.
- E. Session 9822 will always stop waiting if the session that owns the TX enqueue issues a COMMIT statement as session 9822 is the first session in the transaction queue.
- F. Session 8779 may be waiting for a user or application response.
Answer: B,E,F
Explanation:
For this SQL statement and output, we can analyze theEVENTcolumn to understand the type of wait:
B: The event "SQL*Net message from client" typically indicates that the session is waiting for a response from the client. This can be due to a network issue, user response, or an application processing delay.
E: The event "SQL*Net message from client" also implies that the session is idle waiting for the client (a user or an application) to send a request to the server. This event usually indicates that the session is not actively working but is instead waiting for the next command.
F: The wait event "enq: TX - row lock contention" suggests that session 9822 is waiting for a row-level lock held by another session. If the holding session issues a COMMIT or ROLLBACK, the lock will be released, and session 9822 will stop waiting. Since this session is experiencing row lock contention, it implies it's waiting for a specific transaction to complete.
References:
* Oracle Database Reference, 19c
* Oracle Wait Events Documentation
NEW QUESTION # 38
Which application lifecycle phase could be managed reactively?
- A. Testing
- B. Design and development
- C. Production
- D. Deployment
- E. Upgrade or migration
Answer: C
Explanation:
The production phase of the application lifecycle is often managed reactively. While proactive measures and performance tuning are essential, unforeseen issues can arise in production that require immediate attention and resolution. Reactive management involves monitoring performance and responding to issues as they occur, ensuring the application maintains acceptable performance levels for end-users.
References
* Oracle Database 19c Performance Tuning Guide - Reactive Tuning
NEW QUESTION # 39
Which two options are part of a Soft Parse operation?
- A. SQL Row Source Generation
- B. Semantic Check
- C. Shared Pool Memory Allocation
- D. SQL Optimization
- E. Syntax Check
Answer: B
NEW QUESTION # 40
Which two statements are true about space usage in temporary tablespaces?
- A. Lack of temporary tablespace space for sort operations can be prevented by using temporary tablespace groups.
- B. Temporary tablespaces setting Includes quotas to limit temporary space used by a session for that Temporary tablespace.
- C. When a session consumes all temporary tablespace storage, then the session would hang until the temporary space used by that session is cleared.
- D. When a global temporary table instantiation is too large to fit in memory, space is allocated in a temporary tablespace.
- E. A sort will fail if a sort to disk requires more disk space and no additional extent can be found/allocated in/for the sort segment.
Answer: A,D
Explanation:
Regarding space usage in temporary tablespaces, the following statements are true:
* A (Correct):When a global temporary table or a sort operation exceeds the available memory, Oracle Database allocates space in a temporary tablespace to store the temporary data or intermediate results.
* E (Correct):Using temporary tablespace groups can prevent insufficient temporary tablespace for sort operations by providing a collective pool of space from multiple temporary tablespaces, which can be used for user sorting operations.
The other options provided have inaccuracies:
* B (Incorrect):Oracle does not provide a mechanism for setting quotas on temporary tablespaces. Quotas can be set for permanent tablespaces but not for temporary ones.
* C (Incorrect):A sort operation may fail due to insufficient space, but Oracle will attempt to allocate space in the temporary tablespace dynamically. If no space can be allocated, an error is returned rather than a sort failure.
* D (Incorrect):If a session consumes all available temporary tablespace storage, Oracle will not hang the session; it will return an error to the session indicating that it has run out of temporary space.
References:
* Oracle Database Administrator's Guide:Managing Space for Schema Objects
* Oracle Database Concepts:Temporary Tablespaces
NEW QUESTION # 41
Examine these statements and output:
What parameter change activates the generation and use of SQL Plan Directives7
- A. optimizer_capture_sql_plan_baselines_TRUE
- B. optimizer_adaptive_plans=TRUE
- C. optimizer_features_enable=12.2.0.1
- D. optimizer_dynamic_sampling=11
- E. optimizer_adaptive_statistics = TRUE
Answer: E
Explanation:
The optimizer_adaptive_statistics parameter, when set to TRUE, enables the optimizer to use adaptive statistics, such as SQL Plan Directives, to help improve plans by automatically adjusting them based on the actual execution statistics.
References:
* Oracle Database SQL Tuning Guide, 19c
NEW QUESTION # 42
A database supporting a mixed workload is hosted on a server with 64 CPUs.
A large number of free buffer waits and buffer busy waits occur affecting performance.
The buffer cache size was then increased but after a few hours, the same wait events occur more often than before the change.
Examine these parameter settings:
Which two actions can help reduce the number of these waits7
- A. reducing the values of DB_FILE_MULTILOCK_READ_COUNT to 64
- B. increasing the value of DB_FILE_MULTIBLOCK_READ_COUNT to 128
- C. Increasing the size of MEMORYTARGET
- D. increasing the value of DBWRITERPROCESSES to 64,
- E. setting dbwr_io_slaves to 64
Answer: D,E
Explanation:
Given a server with 64 CPUs, if the buffer cache size increase did not alleviate free buffer waits and buffer busy waits, one can look into optimizing I/O and the efficiency of the DB writer processes.
C: Setting the DBWR_IO_SLAVES parameter to a non-zero value, such as the number of CPUs, would initiate I/O slave processes to assist the DB writer process. This can help reduce I/O contention when writing from the buffer cache to disk, particularly for systems without asynchronous I/O capabilities.
D: Increasing the value of DBWRITERPROCESSES enables multiple DB writer processes to be active simultaneously. In a system with many CPUs, such as 64, increasing this value can improve the write throughput to disk and potentially reduce buffer busy waits.
References:
* Oracle Database Reference, 19c
* Oracle Database Performance Tuning Guide, 19c
NEW QUESTION # 43
A Standard Edition production database has performance problems for two hours on the same day each week.
Which tool must you use to diagnose the problem?
- A. Statspack report
- B. Database Replay
- C. SQL Performance Analyzer
- D. AWR Compare Periods report
Answer: A
Explanation:
For a Standard Edition production database, the Statspack tool is available to diagnose performance problems.
The Automatic Workload Repository (AWR) and its related tools like AWR Compare Periods report and SQL Performance Analyzer are features of the Oracle Database Enterprise Edition and are not available in Standard Edition. Database Replay is also a feature of the Enterprise Edition. Statspack is a performance diagnostic tool provided for earlier versions and Standard Editions of the Oracle Database to collect, store, and analyze performance data.
References
* Oracle Database 19c Administrator's Guide - Using Statspack to Diagnose Database Performance Issues
NEW QUESTION # 44
Which two statements are true about cursor sharing?
- A. Adaptive Cursor Sharing requires histograms on filtered columns, used in equality predicates, to allow different execution plans to be generated for statements whose bound values would normally generate different plans at hard parse time.
- B. Adaptive Cursor Sharing guarantees that a suboptimal plan will never be used on any execution of a SQL statement.
- C. Setting cursor_sharing to EXACT prevents Adaptive Cursor Sharing from being used.
- D. Setting optimizer_capture_sql_plan_baselines to TRUE loads all adaptive plans for the same statement into the cursor cache.
- E. Setting Cursor_sharing to FORCE can result in a plan that is suboptimal for the majority of values bound to a bind variable when executing a cursor with one or more bind variables.
Answer: C,E
Explanation:
A: WhenCursor_sharingis set toFORCE, Oracle tries to avoid hard parses by replacing literals in SQL statements with bind variables, even if the original statement didn't include bind variables. This can lead to the use of a single execution plan for multiple executions of a statement with different literal values, which might not be optimal for all executions.
D: Settingcursor_sharingtoEXACTensures that SQL statements must match exactly for them to share a cursor. This setting prevents the use of Adaptive Cursor Sharing (ACS) since ACS relies on the ability to share cursors among similar statements that differ only in their literal values. WithEXACT, there's no cursor sharing for statements with different literals, hence no opportunity for ACS to operate.
References:
* Oracle Database SQL Tuning Guide, 19c
* Oracle Database Reference, 19c
NEW QUESTION # 45
You use SQL Tuning Advisor to tune a given SQL statement.
The analysis eventually results in the implementation of a SQL Profile.
You then generate the new SQL Profile plan and enforce it using a SQL PlanBaselinebut forget to disable the SQLProfile and a few days later you find out that the SQL Profile is generating a new execution plan.
Which two statements are true?
- A. The SQL Plan Baseline must be accepted in order to be used for the execution plan.
- B. The execution plan is the one enforced by the SQL Plan Baseline.
- C. The conflict between the two plan stability methods results in an error.
- D. The execution plan is the one enforced by the SQL Profile.
- E. The existence of two concurrent plan stability methods generates a child cursor for every execution.
- F. The SQL Profiles as well as SQL Plan Baseline are implemented using hints, so they both generate the same plan.
Answer: A,D
Explanation:
When both a SQL Profile and a SQL Plan Baseline are in place, the SQL Profile has a stronger preference and the optimizer is more likely to choose the execution plan from the SQL Profile.
C: A SQL Profile is generally more influential than a SQL Plan Baseline because it contains additional statistics and directives that help the optimizer to generate a more efficient execution plan. If both exist, the optimizer will use the profile's plan unless the baseline's plan is proven to be better through the SQL performance monitoring process.
E: SQL Plan Baselines must be accepted before they can be used by the optimizer. If a SQL Plan Baseline is not accepted, it will not be considered for generating the execution plan. Therefore, the presence of an unaccepted SQL Plan Baseline will not automatically force the optimizer to use its plan.
References:
* Oracle Database SQL Tuning Guide, 19c
* Oracle Database Administrator's Guide, 19c
NEW QUESTION # 46
Which three statements are true about using the in Memory (IM) column store?
- A. It does not require all database data to fit in memory to improve query performance.
- B. It does not improve performance for queries using cached results of function evaluations on columns from the same table.
- C. It does not improve performance for queries that use join groups on columns from different tables.
- D. It can improve OLTP workload performance by avoiding the use of indexes.
- E. It improves performance for queries joining several tables using bloom filter joins.
- F. It does not improve performance for queries using user-defined virtual column results.
Answer: A,D,E
Explanation:
The Oracle In-Memory (IM) column store feature enhances the performance of databases by providing a fast columnar storage format for analytical workloads while also potentially benefiting OLTP workloads.
* C (True): It can improve OLTP workload performance by providing a faster access path for full table scans and reducing the need for indexes in certain scenarios, as the In-Memory store allows for efficient in-memory scans.
* E (True): The In-Memory column store does not require all database data to fit in memory. It can be used selectively for performance-critical tables or partitions, and Oracle Database will manage the population and eviction of data as needed.
* F (True): In-Memory column store can significantly improve performance for queries joining several tables, especially when bloom filters are used, as they are highly efficient with the columnar format for large scans and join processing.
The other options provided are not correct in the context of the In-Memory column store:
* A (False): While In-Memory column store is designed for analytical queries rather than caching results of function evaluations, it does not specifically avoid improving performance for queries using cached results of function evaluations.
* B (False): In-Memory column store can improve the performance of queries that use join groups, which can be used to optimize joins on columns from different tables.
* D (False): In-Memory column store can improve the performance of queries using expressions, including user-defined virtual columns, because it supports expression statistics which help in optimizing such queries.
References:
* Oracle Database In-Memory Guide: In-Memory Column Store in Oracle Database
* Oracle Database In-Memory Guide: In-Memory Joins
* Oracle Database In-Memory Guide: In-Memory Aggregation
NEW QUESTION # 47
Database performance degraded between 23:15 and 23:30 for the last three nights. The awr snapshot interval is one hour. The AODM report contains nothing about this performance problem.
With which tool can you further analyze this problem?
- A. SQL Tuning Advisor
- B. SQL Performance Analyzer
- C. AWR Compare Periods report
- D. Active Session History report
Answer: D
Explanation:
The Active Session History (ASH) report is a tool that provides detailed information about active sessions for the time period specified. Since the AWR snapshot interval is one hour and does not capture the granularity needed for this issue, ASH reports aremore suitable as they contain more granular data for sessions that were active during the period of interest.
References:
* Oracle Database Performance Tuning Guide, 19c
NEW QUESTION # 48
You must write a statement that returns the ten most recent sales. Examine this statement:
Users complain that the query executes too slowly. Examine the statement's current execution plan:
What must you do to reduce the execution time and why?
- A. Enable Adaptive Plans so that Oracle can change the Join method as well as the Join order for this query.
- B. Replace the FETCH FIRST clause with ROWNUM to enable the use of an index on SALES.
- C. Collect a new set of statistics on PRODUCT, CUSTOMERS, and SALES because the current stats are inaccurate.
- D. Create an index on SALES.TIME_ID to force the return of rows in the order specified by the ORDER BY clause.
- E. Create an index on SALES.CUST_ID to force an INDEX RANGE SCAN on this index followed by a NESTED LOOP join between CUSTOMERS and SALES.
Answer: D
Explanation:
The execution plan shows a full table access for the SALES table. To reduce the execution time, creating an index on SALES.TIME_ID would be beneficial as it would allow the database to quickly sort and retrieve the most recent sales without the need to perform a full table scan, which is I/O intensive and slower. By indexing TIME_ID, which is used in the ORDER BY clause, the optimizer can take advantage of the index to efficiently sort and limit the result set to the ten most recent sales.
* B (Incorrect): Replacing FETCH FIRST with ROWNUM would not necessarily improve the performance unless there is an appropriate index that the optimizer can use to avoid sorting the entire result set.
* C (Incorrect): There is no indication that the current statistics are inaccurate; hence, collecting new statistics may not lead to performance improvement.
* D (Incorrect): While adaptive plans can provide performance benefits by allowing the optimizer to adapt the execution strategy, the main issue here is the lack of an index on the ORDER BY column.
* E (Incorrect): Creating an index on SALES.CUST_ID could improve join performance but would not address the performance issue caused by the lack of an index on the ORDER BY column.
References:
* Oracle Database SQL Tuning Guide: Managing Indexes
* Oracle Database SQL Tuning Guide: Using Indexes and Clusters
NEW QUESTION # 49
Accessing the SALES tables causes excessive db file sequential read wait events.
Examine this AWR except:
Now, examine these attributes displayed by querying dba_tables:
Finally, examine these parameter settings:
Which two must both be used to reduce these excessive waits?
- A. Increase PCTFREE for the SALES table.
- B. Coalesce all sales table indexes.
- C. Partition the SALES table.
- D. Compress the SALES table.
- E. Re-create the SALES table.
Answer: C,D
Explanation:
The AWR excerpt points to excessive physical reads on the SALES table and index, suggesting the need for optimizing table storage and access.
Partitioning the SALES table (A) can reduce 'db file sequential read' waits by breaking down the large SALES table into smaller, more manageable pieces. This can localize the data and reduce the I/O necessary for query operations.
Compressing the SALES table (D) can also help reduce I/O by minimizing the amount of data that needs to be read from disk. This can also improve cache utilization and reduce the 'db file sequential read' waits.
References:
* Oracle Database VLDB and Partitioning Guide, 19c
* Oracle Database Administrator's Guide, 19c
These changes are recommended based on Oracle's best practices for managing large tables and reducing I/O waits, ensuring better performance and efficiency.
NEW QUESTION # 50
Which two statements are true about disabling Automatic Shared Memory Management (ASMM)?
- A. The SGA size remains unaffected after disabling ASMM.
- B. It requires a database instance restart to take effect.
- C. Both SGA_TARGET and SGA_MAX_SIZE must be set to zero.
- D. All SGA components excluding fixed SGA and other internal allocations are readjusted immediately after disabling ASMM.
- E. All auto-tuned SGA components are reset to their original user-defined values.
- F. All SGA components retain their current sizes at the time of disabling.
Answer: A,F
Explanation:
When ASMM is disabled, the sizes of the automatically managed SGA components remain at their current values. ASMM is controlled by the SGA_TARGET parameter. If SGA_TARGET is set to a non-zero value, ASMM is enabled and Oracle will automatically manage the sizes of the various SGA components. When ASMM is disabled, by setting SGA_TARGET to zero, the SGA components that were automatically sized will retain their current sizes rather than being reset to their original user-defined values. The overall size of the SGA remains the same unless manually changed by modifying individual component sizes or SGA_MAX_SIZE.
References:
* Oracle Database Administration Guide, 19c
* Oracle Database Performance Tuning Guide, 19c
NEW QUESTION # 51
You need to transport performance data from a Standard Edition to an Enterprise Edition database. What is the recommended method to do this?
- A. Export the data by using the exp utility and parameter file spuexp.par from the Statspack repository and import it by using imp into a dedicated Statspack schema on the destination.
- B. Export the data by using expdp from the ftatspack repository and import it by using impdp into the AWR repository.
- C. Export the data by using expdp from Statspack and import it by using
$ORACLE_HOME/rdbms/admin/awrload into the AWRrepository. - D. Export the data by using the expdp utility and parameter file spuexp.par from the Statspack repository and import it by using impdp into Export the data by using expdp from the Statspack repository and import it by using impdp into the AWR repository.
Answer: A
Explanation:
To transport performance data from an Oracle Database Standard Edition, which uses Statspack, to an Enterprise Edition database, which uses AWR, you must consider the compatibility of data structures and repository schemas between these tools. The recommended method is:
* D (Correct):Export the data using theexputility with a parameter file appropriate for Statspack (like spuexp.par) from the Statspack repository and import it into a dedicated Statspack schema on the destination. Since Statspack and AWR use different schemas, it's not recommended to import Statspack data directly into the AWR repository.
The other options are incorrect because:
* A (Incorrect):expdpis not designed to export from Statspack, andawrloadis intended for loading from an AWR export file, not a Statspack export.
* B (Incorrect):Althoughexpdpandimpdpare used for exporting and importing data, the AWR repository schema is different from the Statspack schema, so importing Statspack data directly into the AWR repository is not recommended.
* C (Incorrect):Usingexpdpto export from Statspack and then importing directly into the AWR repository is not the correct approach due to the schema differences between Statspack and AWR.
References:
* Oracle Database Performance Tuning Guide:Migrating from Statspack to AWR
NEW QUESTION # 52
Which three statements are true about tuning dimensions and details of v$sys_time_model and DB time?
- A. Statspack cannot account for high CPU time when CPU TIME is a Top 10 event in DB time. When CPU time is high, SQL tuning may improve performance.
- B. When WAIT TIME is high, instance tuning may improve performance.
- C. DB Time accounts for all time used by background processes and user sessions.
- D. Systems in which CPU time is dominant need more tuning that those in which WAIT TIME is dominant.
- E. Parse Time Elapsed accounts for successful soft and hard parse operations only.
- F. The proportion of WAIT TIME to CPU TIME always increases with increased system load.
Answer: A,B,C
Explanation:
A: Statspack is a performance diagnostic tool that can help identify high CPU usage issues. High CPU time may indicate that SQL statements need to be tuned for better performance.
D: High wait times can often be reduced by instance tuning, such as adjusting database parameters or improving I/O performance.
F: DB Time is a cumulative time metric that includes the time spent by both user sessions and background processes executing database calls.References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Concepts, 19c
NEW QUESTION # 53
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