Provide Oracle 1z1-084 Dumps Updated Feb 14, 2025 With 57 QA's [Q30-Q55]

Provide Oracle 1z1-084 Dumps Updated Feb 14, 2025 With 57 QA's

Latest 1z1-084 Dumps for Success in Actual Oracle Certified

Oracle 1Z0-084 is an exam that tests the knowledge and skills of individuals in the area of Oracle Database 19c Performance and Tuning Management. 1z1-084 exam is designed for individuals who are responsible for managing and tuning the performance of Oracle Database 19c. It is an important certification for database administrators and developers who want to demonstrate their expertise in performance tuning.

Oracle 1Z0-084 exam consists of multiple-choice questions that are designed to evaluate the candidate's knowledge and understanding of Oracle Database 19c Performance and Tuning Management. 1z1-084 exam is conducted online and can be taken from anywhere in the world. 1z1-084 exam is time-bound, and candidates are required to complete it within the specified time limit.

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. 1z1-084 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.

 

NEW QUESTION # 30
Which two statements are true about the use and monitoring of Buffer Cache Hit ratios and their value in tuning Database I/O performance?

• A. The buffer cache advisory view v$db_cache_advice provides advice on cache hit ratios appropriate for the instance workload.
• B. Both the RECYCLE and KEEP buffer caches should always have a very high cache hit ratio.
• C. The performance of workloads that primarily generate full table scans and fast full index scans are always affected by the cache hit ratio.
• D. A 99% cache hit ratio can be observed for database instances which have very poor I/O performance.
• E. A 60% cache hit ratio can be observed for database instances which have very good I/O performance.

Answer: A,D

NEW QUESTION # 31
Examine this AWRreport excerpt:

You must reduce the impact of database I/O, without increasing buffer cache size and without modifying the SQL statements.
Which compression option satisfies this requirement?

• A. COLUMN STORE COMPRESS FOR QUERY HIGH
• B. STORE COMPRESS
• C. ROW STORE COMPRESS ADVANCED
• D. MN STORE COMPRESS FOR QUERY LOW

Answer: C

Explanation:
To reduce the impact of database I/O without increasing the size of the buffer cache and without modifying SQL statements, you can use table compression. Among the given options,ROW STORE COMPRESS ADVANCEDis the most suitable form of table compression to satisfy this requirement.
Advanced row compression (ROW STORE COMPRESS ADVANCED) is designed to work well with all supported types of data, whether it's OLTP or data warehouse environments. It offers a higher level of compression than basic table compression (ROW STORE COMPRESS BASIC)without significant overhead during DML operations. This feature can help reduce the amount of I/O required to retrieve data by storing it more efficiently on disk.
* A, B, D:WhileCOLUMN STORE COMPRESS FOR QUERY HIGHandROW STORE
COMPRESSare both valid compression types,COLUMN STORE COMPRESS FOR QUERY
* HIGHapplies to the In-Memory column store and is not available in all versions and editions, andROW STORE COMPRESSis less advanced thanROW STORE COMPRESS ADVANCED.
References:
* Oracle Database Concepts Guide:Table Compression
* Oracle Database Performance Tuning Guide:Row Compression

NEW QUESTION # 32
Which two statements are true about disabling Automatic Shared Memory Management (ASMM)?

• A. All auto-tuned SGA components are reset to their original user-defined values.
• B. All SGA components retain their current sizes at the time of disabling.
• C. The SGA size remains unaffected after disabling ASMM.
• D. All SGA components excluding fixed SGA and other internal allocations are readjusted immediately after disabling ASMM.
• E. It requires a database instance restart to take effect.
• F. Both SGA_TARGET and SGA_MAX_SIZE must be set to zero.

Answer: B,C

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 # 33
During which application lifecycle phase do you take baselines?

• A. Production
• B. Migration or upgrade
• C. Design and development
• D. Testing
• E. Deployment

Answer: A

Explanation:
Baselines are typically taken during the production phase of the application lifecycle. They provide a snapshot of performance metrics under normal operating conditions which can be used for comparison against future performance. Baselines are essential for understanding how the system performs under its typical workload and for detecting deviations from this expected performance over time, especially after changes like migrations, upgrades, or significant changes in user activity.
References
* Oracle Database 19c Performance Tuning Guide - Managing Performance Through Baselines

NEW QUESTION # 34
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 tine excludes the time spent waiting for a CPU in the operating system run queue.
• C. DB time includes the time spent executing the RMAN backup and restore command.
• 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 # 35
Examine these statements and output:

What parameter change activates the generation and use of SQL Plan Directives7

• A. optimizer_features_enable=12.2.0.1
• B. optimizer_capture_sql_plan_baselines_TRUE
• C. optimizer_adaptive_statistics = TRUE
• D. optimizer_dynamic_sampling=11
• E. optimizer_adaptive_plans=TRUE

Answer: C

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 # 36
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 execution plan is the one enforced by the SQL Profile.
• B. The SQL Profiles as well as SQL Plan Baseline are implemented using hints, so they both generate the same plan.
• C. The existence of two concurrent plan stability methods generates a child cursor for every execution.
• D. The SQL Plan Baseline must be accepted in order to be used for the execution plan.
• E. The conflict between the two plan stability methods results in an error.
• F. The execution plan is the one enforced by the SQL Plan Baseline.

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 # 37
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. Replace the FETCH FIRST clause with ROWNUM to enable the use of an index on SALES.
• B. Enable Adaptive Plans so that Oracle can change the Join method as well as the Join order for this query.
• C. Create an index on SALES.TIME_ID to force the return of rows in the order specified by the ORDER BY clause.
• D. Collect a new set of statistics on PRODUCT, CUSTOMERS, and SALES because the current stats are inaccurate.
• 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: C

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 # 38
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 expdp from the ftatspack repository and import it by using impdp into the AWR repository.
• B. 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.
• C. 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.
• D. Export the data by using expdp from Statspack and import it by using $ORACLE_HOME/rdbms/admin
  /awrload into the AWR repository.

Answer: B

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 the exp utility 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): expdp is not designed to export from Statspack, and awrload is intended for loading from an AWR export file, not a Statspack export.
* B (Incorrect): Although expdp and impdp are 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): Using expdp to 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 # 39
Which three types of statistics are captured by statspack with snap level 6?

• A. Parent and child latches
• B. Enqueue statistics
• C. Plan usage data
• D. Segment-level statistics
• E. Optimizer execution plans
• F. Parent and child latches

Answer: B,D,F

Explanation:
Statspack is a performance diagnostic tool provided by Oracle prior to the introduction of the Automatic Workload Repository (AWR). At snap level 6, Statspack captures the following types of statistics:
* A (Correct):Parent and child latches are captured. Latch statistics provide information about contention for latches, which are low-level serialization mechanisms used by Oracle.
* E (Correct):Enqueue statistics, which provide information on the waits for locks that manage the concurrency between users.
* F (Correct):Segment-level statistics, which provide detailed information on database segments such as tables, indexes, etc., to identify I/O and contention issues.
* C (Incorrect):While optimizer execution plans are an essential aspect of performance tuning, detailed execution plan capture is not part of the Statspack report at level 6.
* D (Incorrect):Plan usage data refers to how frequently a plan is being used, which is more associated with AWR and not typically captured in Statspack reports.
References:
* Oracle Database Performance Tuning Guide:Using Statspack

NEW QUESTION # 40
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 parameter to 192G.
• B. Set DB_FLASH_CACHE_SIZE to 256G and change device /dev/sdk to 128G.
• C. Set DB_FLASH_CACHE_SIZE parameter to 128G, 64G.
• D. Disable Automatic Memory Management and set SGA_TARGET to 256G.
• E. Set DB_FLASH_CACHE_SIZE to 192G and MEMORY_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 # 41
Examine this statement and output:

Which two situations can trigger this error?

• A. There is a file in the capture directory.
• B. The instance is unable to access the capture directory.
• C. The syntax is incomplete.
• D. The user lacks the required privileges to execute the DBMS WORKLOAD CAPTURE package or the directory.
• E. The capture directory is part of the root file system.

Answer: B,D

Explanation:
The ORA-15505 error indicates that the instance encountered errors while trying to access the specified directory. This could be due to:
A: Insufficient privileges: The user attempting to start the workload capture might not have the required permissions to execute the DBMS_WORKLOAD_CAPTURE package or to read/write to the directory specified.
E: Accessibility: The database instance may not be able to access the directory due to issues such as incorrect directory path, directory does not exist, permission issues at the OS level, or the directory being on a file system that's not accessible to the database instance.
References:
* Oracle Database Error Messages, 19c
* Oracle Database Administrator's Guide, 19c

NEW QUESTION # 42
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_POLICYADAPTIVE
• D. Increasing DB_CACHESIZE to 1 G
• E. Setting DB_KEEP_CACHE_SIZE to at least 50M
• F. Setting PARALLEL_DEGREE_POLICYAUTO

Answer: A,D

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_TARGET is 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): Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to 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): Increasing DB_CACHE_SIZE to 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: Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to 50 without adjusting the overall size of the cache might still not be sufficient if the DB_CACHE_SIZE is not large enough to hold the big tables.
* B: Setting DB_KEEP_CACHE_SIZE to at least 50M only specifies a separate buffer pool for objects with the KEEP cache attribute and does not affect Big Table caching.
* E: and F: Changing the PARALLEL_DEGREE_POLICY to ADAPTIVE or AUTO influences 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 # 43
You must produce a consolidated formatted trace file by combining all trace files generated by all clients for a single service.
Which combination of utilities does this?

• A. Autotrace and TKPROF
• B. Trace Analyzer and Tracsess
• C. Trcsess and TKPROF
• D. TKPROF and Trace Analyzer

Answer: C

Explanation:
To produce a consolidated formatted trace file from multiple trace files generated by all clients for a single service, the combination oftrcsessandTKPROFutilities is used. Thetrcsessutility consolidates trace files based on specified criteria such as session, client identifier, or service name. This results in a single trace file that combines the desired tracing information. Next,TKPROFis used to format the output of the trace file generated bytrcsess, providing a readable summary of the trace, including execution counts, execution times, and SQL statement text along with execution plans.
Steps:
* Usetrcsessto combine trace files:
* Command:trcsess output=consolidated.trc service=your_service_name *.trc
* UseTKPROFto format the consolidated trace file:
* Command:tkprof consolidated.trc output.txt explain=user/password sys=no sort=prsela,fchela References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Utilities, 19c

NEW QUESTION # 44
Buffer cache access is too frequent when querying the SALES table. Examine this command which executes successfully:
ALTER TABLE SALES SHRINK SPACE;
For which access method does query performance on sales improve?

• A. db file scattered read
• B. index range scan
• C. db file sequential read
• D. index full scan

Answer: C

Explanation:
The SHRINK SPACE operation compacts the table, which can reduce fragmentation and thus improve performance for sequential reads of the table. This operation could improve full table scans, which are typically associated with db file sequential read wait events.
References:
* Oracle Database Administrator's Guide, 19c

NEW QUESTION # 45
The CURS0R_SHARING and OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES parameters are set to default. The top five wait events in an awr report are due to a large number of hard parses because of several almost identical SQL statements.
Which two actions could reduce the number of hard parses?

• A. Set OPTIMIZER_CAPTURE_SQL_PLAN_BASELINESto TRUE.
• B. Set the CURSOR_SHARING parameter to FORCE.
• C. Increase the size of the library cache.
• D. Create the KEEP cache and cache tables accessed by the SQL statements.
• E. Create the RECYCLE cache and cache tables accessed by the SQL statements.

Answer: B,C

Explanation:
To reduce the number of hard parses due to several almost identical SQL statements, you can take the following actions:
* C (Correct):Increasing the size of the library cache can help reduce hard parses by providing more
* memory to store more execution plans. This allows SQL statements to be shared more effectively.
* E (Correct):Setting theCURSOR_SHARINGparameter toFORCEwill cause Oracle to replace literals in SQL statements with bind variables, which can significantly reduce the number of hard parses by making it more likely that similar SQL statements will share the same execution plan.
The other options do not directly impact the number of hard parses:
* A (Incorrect):Creating the KEEP cache and caching tables accessed by the SQL statements can improve performance for those tables, but it does not directly reduce the number of hard parses.
* B (Incorrect):Creating the RECYCLE cache and caching tables accessed by the SQL statements can make it more likely that objects will be removed from the cache quickly, which does not help with hard parse issues.
* D (Incorrect):SettingOPTIMIZER_CAPTURE_SQL_PLAN_BASELINEStoTRUEcan help stabilize SQL execution plans but will not reduce the number of hard parses. This parameter is used to automatically capture SQL plan baselines for repeatable SQL statements, which can prevent performance regressions due to plan changes.
References:
* Oracle Database Performance Tuning Guide:Minimizing Hard Parses
* Oracle Database SQL Tuning Guide:CURSOR_SHARING

NEW QUESTION # 46
Examine these commands, which execute successfully:

Which statement is true?

• A. AWR- snapshots in all pluggable databases will be purgedautomatically after every 60 mins.
• B. ADDM, AWR, and ASH reports can be purged automatically.
• C. AWR snapshots can be purged manually in pluggable databases.
• D. AD DM is enabled for all pluggable databases.

Answer: C

Explanation:
TheDBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGSprocedure allows setting attributes related to AWR snapshots. While the interval setting controls the frequency of snapshot generation, purging them is a separate process that can be managed either automatically (with retention settings) or manually.References:
* Oracle Database PL/SQL Packages and Types Reference, 19c
* Oracle Multitenant Administrator's Guide, 19c

NEW QUESTION # 47
Which two types of performance problems are reported by ADDM for PDBS?

• A. User I/O waits
• B. Excessive checkpoint writes
• C. I/O capacity limits
• D. Top SQL statements
• E. SGA sizing issues

Answer: A,C

Explanation:
The Automatic Database Diagnostic Monitor (ADDM) analyzes and reports on various types of performance problems. For Pluggable Databases (PDBs), it can identify issues such as I/O capacity limits which may hinder the overall performance by causing bottlenecks. Additionally, ADDM can report on user I/O waits, which can indicate performance issues related to the time it takes for user queries to read data from the disk.
References:
* Oracle Multitenant Administrator's Guide, 19c
* Oracle Database Performance Tuning Guide, 19c

NEW QUESTION # 48
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 can improve OLTP workload performance by avoiding the use of indexes.
• C. It does not improve performance for queries using cached results of function evaluations on columns from the same table.
• D. It does not improve performance for queries that use join groups on columns from different tables.
• 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,B,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 # 49
An Oracle 19c database uses default values for all optimizer initialization parameters.
After a table undergoes partition maintenance, a large number of wait events occur for:
cursor: pin S wait on X
Which command reduces the number of these wait events?

• A. ALTER SYSTEM SET SESSION CACHED CURSORS = 500;
• B. ALTER SYSTEM SET CURSOR_SHARING = FORCE;
• C. ALTER SYSTEM SET CURSOR_INVALIDATION = DEFERRED;
• D. ALTER SYSTEM SET CURSOR_SPACE_FOR_TIME - TRUE;

Answer: C

Explanation:
The cursor: pin S wait on X wait event suggests contention for a cursor pin, which is associated with mutexes (a type of locking mechanism) that protect the library cache to prevent concurrent modifications.
This issue can often be alleviated by deferring the invalidation of cursors until the end of the call to reduce contention. The correct command to use would be:
* C (Correct): ALTER SYSTEM SET CURSOR_INVALIDATION=DEFERRED; This setting defers the invalidation of dependent cursors until the end of the PL/SQL call, which can reduce the cursor: pin S wait on X wait events.
The other options are incorrect in addressing this issue:
* A (Incorrect): Setting CURSOR_SHARING to FORCE makes the optimizer replace literal values with bind variables. It doesn't address the contention for cursor pins directly.
* B (Incorrect): CURSOR_SPACE_FOR_TIME=TRUE aims to reduce the parsing effort by keeping cursors for prepared statements open. It may increase memory usage but does not directly resolve cursor: pin S wait on X waits.
* D (Incorrect): Increasing SESSION_CACHED_CURSORS caches more session cursors but doesn't necessarily prevent the contention indicated by the cursor: pin S wait on X wait events.
References:
* Oracle Database Reference: CURSOR_INVALIDATION
* Oracle Database Performance Tuning Guide: Reducing Cursor Invalidation

NEW QUESTION # 50
Which two statements are true about the use and monitoring of Buffer Cache Hit ratios and their value in tuning Database I/O performance?

• A. The buffer cache advisory view v$db_cache_advice provides advice on cache hit ratios appropriate for the instance workload.
• B. Both the RECYCLE and KEEP buffer caches should always have a very high cache hit ratio.
• C. The performance of workloads that primarily generate full table scans and fast full index scans are always affected by the cache hit ratio.
• D. A 99% cache hit ratio can be observed for database instances which have very poor I/O performance.
• E. A 60% cache hit ratio can be observed for database instances which have very good I/O performance.

Answer: A,D

Explanation:
A high buffer cache hit ratio typically indicates that the database is effectively using the buffer cache and does not often need to read data from disk. However, this metric alone is not a reliable indicator of the I/O performance of the database for several reasons:
* Full table scans and fast full index scans (A) can bypass the buffer cache by design if the blocks are not
* deemed reusable shortly, which can impact the cache hit ratio.
* A high cache hit ratio (B) can be misleading if the database performance is poor due to other factors, such as inefficient queries or contention issues.
* The buffer cache advisory (C) is a more valuable tool for understanding the potential impact of different cache sizes on the database's I/O performance. It simulates scenarios with different cache sizes and provides a more targeted recommendation.
* The RECYCLE and KEEP buffer caches (D) are specialized caches designed for certain scenarios.
While high hit ratios can be beneficial, they are not universally required; some workloads might not be significantly impacted by lower hit ratios in these caches.
* A lower cache hit ratio (E) does not necessarily mean poor I/O performance. In some cases, a system with a well-designed storage subsystem and efficient queries might perform well even with a lower cache hit ratio.
References
* Oracle Database 19c Performance Tuning Guide - Buffer Cache Hit Ratio
* Oracle Database 19c Performance Tuning Guide - v$db_cache_advice

NEW QUESTION # 51
What is the right time to stop tuning an Oracle database?

• A. When all the concurrency waits are eliminated from the Top 10
• B. When the allocated budget for performance tuning has been exhausted
• C. When the I/O is less than 10% of the DB time
• D. When the buffer cache and library cache hit ratio is above 95%

Answer: B

Explanation:
The right time to stop tuning an Oracle database is often determined by the point of diminishing returns - when the cost of further tuning (in terms of time, resources, or money) exceeds the performance benefits gained.
This is often related to the budget allocated for performance tuning.
* A (Correct):When the allocated budget for performance tuning has been exhausted, it may be time to stop tuning unless the benefits of further tuning justify requesting additional budget.
* B (Incorrect):Eliminating all concurrency waits from the Top 10 is an unrealistic goal since some waits are inevitable and can occur due to application design, which might not be possible to eliminate completely.
* C (Incorrect):The buffer cache and library cache hit ratio being above 95% does not necessarily indicate that the database is fully optimized. Hit ratios are not reliable indicators of database performance and should not be used as sole criteria to end tuning efforts.
* D (Incorrect):Having I/O less than 10% of DB time is not a definitive indicator to stop tuning. It is essential to consider the overall performance goals and whether they have been met rather than focusing solely on I/O metrics.
References:
* Oracle Database Performance Tuning Guide:Introduction to Performance Tuning
* Oracle Database 2 Day + Performance Tuning Guide:Understanding the Tuning Process

NEW QUESTION # 52
You need to collect and aggregate statistics for the ACCTG service and PAYROLL module, and execute:

Where do you find the output of this command?

• A. By viewing V$SERV_MOD_ACT_STATS
• B. By viewing V$SERVICE_STATS
• C. In $ORACLE_BASE/diag/rdbms/<db unique name>/<instance name>/trace
• D. In the current working directory

Answer: A

Explanation:
When you enable statistics gathering for a specific service and module using DBMS_MONITOR.SERV_MOD_ACT_STAT_ENABLE, the output is aggregated and can be viewed using theV$SERV_MOD_ACT_STATSdynamic performance view. This view contains the cumulative statistics of database activity broken down by service and module, which is exactly what you collect when executing the provided command.
* B (Incorrect):While many types of trace files are located in the Diagnostic Destination directory (
$ORACLE_BASE/diag), the aggregated statistics for services and modules are not written to trace files but are instead viewable through dynamic performance views.
* C (Incorrect):TheV$SERVICE_STATSview provides service-level statistics but does not provide the
* combined service/module-level breakdown.
* D (Incorrect):The output of the PL/SQL block is not written to a file in the current working directory; it is stored in the data dictionary and accessible via dynamic performance views.
References:
* Oracle Database PL/SQL Packages and Types Reference:DBMS_MONITOR
* Oracle Database Reference:V$SERV_MOD_ACT_STATS

NEW QUESTION # 53
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 DBWRITERPROCESSES to 64,
• C. setting dbwr_io_slaves to 64
• D. Increasing the size of MEMORYTARGET
• E. increasing the value of DB_FILE_MULTIBLOCK_READ_COUNT to 128

Answer: B,C

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 # 54
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. Replace the FETCH FIRST clause with ROWNUM to enable the use of an index on SALES.
• B. Enable Adaptive Plans so that Oracle can change the Join method as well as the Join order for this query.
• C. Create an index on SALES.TIME_ID to force the return of rows in the order specified by the ORDER BY clause.
• D. Collect a new set of statistics on PRODUCT, CUSTOMERS, and SALES because the current stats are inaccurate.
• 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: C

Explanation:
The execution plan shows a full table access for theSALEStable. To reduce the execution time, creating an index onSALES.TIME_IDwould 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 theORDER BYclause, the optimizer can take advantage of the index to efficiently sort and limit the result set to the ten most recent sales.
* B (Incorrect):ReplacingFETCH FIRSTwithROWNUMwould 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 theORDER BYcolumn.
* E (Incorrect):Creating an index onSALES.CUST_IDcould improve join performance but would not address the performance issue caused by the lack of an index on theORDER BYcolumn.
References:
* Oracle Database SQL Tuning Guide:Managing Indexes
* Oracle Database SQL Tuning Guide:Using Indexes and Clusters

NEW QUESTION # 55
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