Practice Oracle Database 19c 1Z0-084 exam. Online Exam Practice Tests with detailed explanations! Pass 1Z0-084 with confidence!
1Z0-084 - Oracle Database 19c Performance and Tuning Management Practice Tests 2026 | ValidTorrent
NEW QUESTION # 13
Which two statements are true about session wait information contained in v$session or v$session_wait?
- A. Rows for sessions that are currently waiting have their wait time incremented every microsecond.
- B. Rows for sessions that are not waiting might contain the actual wait time for the last event for which they waited.
- C. Rows for sessions that are currently waiting have a wait time of 0.
- D. Rows for sessions that are not waiting always contain the total wait time since the session started.
- E. Rows for sessions displaying WAITED UNKNOWN TIME in the STATE column indicate that the session is still waiting.
Answer: B,C
Explanation:
In theV$SESSIONview, Oracle provides information about the session waits:
B: When theWAIT_TIMEcolumn has a value of 0, it signifies that the session is currently waiting for a resource. This column represents the duration of the current or last wait.
C: If the session is not actively waiting, theWAIT_TIMEcolumn shows the time the session spent waiting for the last wait event. If theSTATEcolumn is showing "WAITED KNOWN TIME", it means the session is not currently waiting, but it indicates the time for which it had waited.
References:
* Oracle Database Reference, 19c
* Oracle Database Performance Tuning Guide, 19c
NEW QUESTION # 14
Examine these commands, which execute successfully:
Which statement is true?
- A. AWR snapshots can be purged manually in pluggable databases.
- B. AD DM is enabled for all pluggable databases.
- C. AWR- snapshots in all pluggable databases will be purgedautomatically after every 60 mins.
- D. ADDM, AWR, and ASH reports can be purged automatically.
Answer: A
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 # 15
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. Setting DB_KEEP_CACHE_SIZE to at least 50M
- B. Setting PARALLEL_DEGREE_POLICYAUTO
- C. Increasing DB_CACHESIZE to 1 G
- D. Setting PARALLEL_DEGREE_POLICYADAPTIVE
- E. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 50
- F. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 25
Answer: C,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 # 16
What is the right time to stop tuning an Oracle database?
- A. When the I/O is less than 10% of the DB time
- B. When the allocated budget for performance tuning has been exhausted
- C. When all the concurrency waits are eliminated from the Top 10
- 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 # 17
18. The application provider has given full indications regarding the procedure to collect statistics.
To reduce the space used in the SYSAUX tablespace, you want to prevent the optimizer statistics Advisor from running.
Which method will allow you to do this?
- A. Set the parameter OPTIMIZER_ADAPTIVE_STATISTICS to FALSE.
- B. Use DBMS STATS.DROP ADVISOR TASK to drop the AUTO_STATS_ADVISOR_TASK task.
- C. Set the AUTO_STATS_ADVISOR_TASK global statistics preference to FALSE.
- D. Use DBMS_AUTO_TASK_ADMIN. DISABLE to disable the AUTO_STATS_ADVISOR_TASK task.
Answer: D
Explanation:
The Oracle Optimizer statistics advisor, which is part of the automated tasks framework, can be disabled using the DBMS_AUTO_TASK_ADMIN package. This will prevent it fromrunning and thus reduce space usage in the SYSAUX tablespace.References:
* Oracle Database PL/SQL Packages and Types Reference, 19c
NEW QUESTION # 18
Which three statements are true about using the in Memory (IM) column store?
- A. It does not improve performance for queries using cached results of function evaluations on columns from the same table.
- B. It does not improve performance for queries using user-defined virtual column results.
- C. It does not require all database data to fit in memory to improve query performance.
- D. It improves performance for queries joining several tables using bloom filter joins.
- E. It can improve OLTP workload performance by avoiding the use of indexes.
- F. It does not improve performance for queries that use join groups on columns from different tables.
Answer: C,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 # 19
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. Setting DB_KEEP_CACHE_SIZE to at least 50M
- B. Setting PARALLEL_DEGREE_POLICYAUTO
- C. Increasing DB_CACHESIZE to 1 G
- D. Setting PARALLEL_DEGREE_POLICYADAPTIVE
- E. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 50
- F. Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 25
Answer: C,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_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 # 20
Which two Oracle Database features use database services?
- A. Oracle SQL Performance Management
- B. Database Resource Manager
- C. Oracle Automatic Reoptimization
- D. Oracle Scheduler
- E. Oracle SQL Tuning Advisor
Answer: B,D
Explanation:
Database services in Oracle are used to manage how resources are allocated and how workloads are managed within the database. The features that use database services are:
* B (Correct):Database Resource Manager (DBRM) uses services to control resource allocation to different workloads. It ensures that resources are assigned to the most critical tasks first, based on the service associated with the workload.
* E (Correct):Oracle Scheduler can also utilize database services. Jobs in Oracle Scheduler can be assigned to different services to control resource allocation and prioritization.
The other features mentioned are related to SQL performance but do not directly utilize database services in the way Resource Manager and Scheduler do:
* A:Oracle Automatic Reoptimization is a feature that allows the database to automatically improve the execution plan of a SQL statement after it is executed, based on the actual performance metrics, but it does not directly use database services.
* C:Oracle SQL Performance Management involves various components of SQL tuning and monitoring, but it does not use database services to operate.
* D:Oracle SQL Tuning Advisor provides advice on how to tune SQL queries for better performance.
While it can be used in conjunction with services for managing and analyzing workloads, it doesn't use services in its core functionality.
References:
* Oracle Database Administrator's Guide:Administering Services
* Oracle Database Administrator's Guide:Managing Resources with Oracle Database Resource Manager
* Oracle Database Scheduler Developer's Guide:Using the Scheduler
NEW QUESTION # 21
Which two statements are true about cursor sharing?
- A. Adaptive Cursor Sharing guarantees that a suboptimal plan will never be used on any execution of a SQL statement.
- B. 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.
- 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 # 22
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. Collect a new set of statistics on PRODUCT, CUSTOMERS, and SALES because the current stats are inaccurate.
- B. Replace the FETCH FIRST clause with ROWNUM to enable the use of an index on SALES.
- C. 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.
- D. Enable Adaptive Plans so that Oracle can change the Join method as well as the Join order for this query.
- E. Create an index on SALES.TIME_ID to force the return of rows in the order specified by the ORDER BY clause.
Answer: E
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 # 23
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$db_cache_advice
NEW QUESTION # 24
Examine this output of a query of VSPGA_TAPGET_ADVICE:
Which statements is true'
- A. With a target of 800 MB or more, all one-pass execution work areas would be eliminated.
- B. PGAA_AGGREGATE should be set to at least 800 MB.
- C. GGREGATE_TARGET should be set to at least 700 MB.
- D. With a target of 700 MB or more, all multipass executions work areas would be eliminated.
Answer: A
Explanation:
The query output from V$PGA_TARGET_ADVICE provides tuning information for the PGA (Program Global Area). Let's break it down step by step:
Key Columns in the Output:
* TARGET_MB:
* Represents the hypothetical PGA_AGGREGATE_TARGET values (in megabytes) evaluated by Oracle.
* CACHE_HIT_PERC:
* The percentage of work areas that could execute in-memory (optimal execution) without requiring temporary disk writes.
* Higher percentages indicate fewer work areas requiring disk I/O.
* ESTD_OVERALLOC_COUNT:
* The estimated number of work areas that need to go to disk (multipass operations or overallocations).
Observations from the Data:
* At TARGET_MB = 700 MB:
* The CACHE_HIT_PERC is 68%.
* The ESTD_OVERALLOC_COUNT is 30. This indicates that some multipass work areas still exist.
* At TARGET_MB = 800 MB:
* The CACHE_HIT_PERC rises to 74%.
* The ESTD_OVERALLOC_COUNT drops to 0. This indicates that no work areas require multipass execution.
* At TARGET_MB = 900 MB and above:
* The CACHE_HIT_PERC increases slightly to 82%-84%.
* The ESTD_OVERALLOC_COUNT remains 0, meaning that all work areas are now either optimal or one-pass.
Why D is Correct:
* At 800 MB or more, the ESTD_OVERALLOC_COUNT is 0, indicating that all one-pass execution work areas are eliminated.
* A one-pass execution requires temporary disk I/O for intermediate results, but with sufficient PGA, these are no longer necessary.
Why Other Options Are Incorrect:
* Option A:
* It mentions all multipass executions work areas would be eliminated at 700 MB. This is incorrect because, at 700 MB, the ESTD_OVERALLOC_COUNT is still 30, indicating some multipass work areas still exist.
* Option B:
* Suggests setting the PGA_AGGREGATE_TARGET to at least 800 MB, which is partially correct but does not address the elimination of one-pass execution.
* Option C:
* Suggests setting the PGA_AGGREGATE_TARGET to at least 700 MB, which is not sufficient to eliminate all one-pass executions, as shown by the ESTD_OVERALLOC_COUNT of 30.
NEW QUESTION # 25
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. Create the RECYCLE cache and cache tables accessed by the SQL statements.
- B. Set the CURSOR_SHARING parameter to FORCE.
- C. Increase the size of the library cache.
- D. Set OPTIMIZER_CAPTURE_SQL_PLAN_BASELINESto TRUE.
- E. Create the KEEP 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 # 26
You want to reduce the amount of db file scattered read that is generated in the database.You execute the SQL Tuning Advisor against the relevant workload. Which two can be part of the expected result?
- A. recommendations regarding the creation of materialized views
- B. recommendations regarding the creation of SQL Patches
- C. recommendations regarding the creation of additional indexes
- D. recommendations regarding partitioning the tables
- E. recommendations regarding rewriting the SQL statements
Answer: A,C
Explanation:
The SQL Tuning Advisor provides recommendations for improving SQL query performance. This may include suggestions for creating additional indexes to speed up data retrieval and materialized views to precompute and store query results.References:
* Oracle Database SQL Tuning Guide, 19c
NEW QUESTION # 27
Examine this output of a query of VSPGA_TAPGET_ADVICE:
Which statements is true'
- A. With a target of 800 MB or more, all one-pass execution work areas would be eliminated.
- B. PGAA_AGGREGATE should be set to at least 800 MB.
- C. GGREGATE_TARGET should be set to at least 700 MB.
- D. With a target of 700 MB or more, all multipass executions work areas would be eliminated.
Answer: D
Explanation:
The V$PGA_TARGET_ADVICE view provides advice on potential performance improvements by adjusting the PGA_AGGREGATE_TARGET parameter. The column ESTD_OVERALLOC_COUNT indicates the estimated number of work areas that would perform multiple passes if the PGA_AGGREGATE_TARGET were set to the size in the TARGET_MB column.
A: According to the output, at the target of 700 MB, the ESTD_OVERALLOC_COUNT is 30. This suggests that if PGA_AGGREGATE_TARGET is set to 700 MB, 30 multipass execution work areas would be required. If we look further down, at the target of 800 MB, the ESTD_OVERALLOC_COUNT is 0, indicating that increasing PGA_AGGREGATE_TARGET to 800 MB or more would eliminate the need for multipass executions, not at 700 MB as initially suggested by the option. Hence, the verified answer derived from the data is slightly nuanced; it should be 800 MB to eliminate all multipass executions.
References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Reference, 19c
NEW QUESTION # 28
Examine this AWR report 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. ROW STORE COMPRESS ADVANCED
- B. STORE COMPRESS
- C. MN STORE COMPRESS FOR QUERY LOW
- D. COLUMN STORE COMPRESS FOR QUERY HIGH
Answer: D
Explanation:
The question asks to reduce database I/O impact without increasing the buffer cache size or modifying SQL statements. This indicates a need to reduce the physical I/O required to access the data. Let's analyze the scenario and the options.
Analysis of the AWR Report:
* Top Wait Events:
* The top foreground wait event is db file sequential read, which accounts for 40.4% of DB time.
This indicates significant physical I/O operations, primarily single-block reads, which are typically associated with index access.
* Reducing the physical I/O associated with db file sequential read can significantly improve performance.
* SQL Ordered by Reads:
* The SQL consuming the most reads involves high physical I/O. This confirms the need to reduce I
/O overhead by compressing data efficiently to minimize physical reads.
Compression Techniques and Their Suitability:
* A. COLUMN STORE COMPRESS FOR QUERY LOW:
* This option is a columnar compression method that optimizes for query performance but provides less compression compared to the HIGH option. While effective, it is not as suitable as FOR QUERY HIGH for reducing I/O.
* B. STORE COMPRESS:
* This is the basic compression option for tables and does not offer the advanced capabilities required for reducing significant physical I/O for queries.
* C. ROW STORE COMPRESS ADVANCED:
* This is a row-level compression that is suitable for OLTP workloads. While it reduces storage, it does not reduce query-related I/O as effectively as columnar compression.
* D. COLUMN STORE COMPRESS FOR QUERY HIGH (Correct Option):
* This is the most effective option for reducing query-related I/O. It:
* Uses columnar compression to reduce the size of data stored on disk.
* Reduces the number of physical reads by compressing data highly, meaning fewer blocks need to be read.
* Optimizes query performance for analytical workloads, which aligns with the scenario described in the AWR report.
Why COLUMN STORE COMPRESS FOR QUERY HIGH Is the Best Fit:
* It is designed to improve query performance by minimizing the amount of I/O required.
* Suitable for environments with heavy read operations (as indicated by the db file sequential read waits).
* Does not require changes to SQL or buffer cache size, adhering to the constraints in the question.
Reference to Oracle Documentation:
* Oracle Database 19c Performance Tuning Guide:
* Section: Using Compression to Reduce Storage and I/O Requirements.
* Discussion of columnar compression techniques for reducing I/O in query-intensive environments.
* Oracle Advanced Compression Documentation:
* Details on COLUMN STORE COMPRESS FOR QUERY HIGH and its benefits for analytical workloads.
NEW QUESTION # 29
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 the current working directory
- D. In $ORACLE_BASE/diag/rdbms/<db unique name>/<instance name>/trace
Answer: A
Explanation:
When you enable statistics gathering for a specific service and module using DBMS_MONITOR.SERV_MOD_ACT_STAT_ENABLE, the output is aggregated and can be viewed using theV$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 # 30
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. STORE COMPRESS
- B. MN STORE COMPRESS FOR QUERY LOW
- C. COLUMN STORE COMPRESS FOR QUERY HIGH
- D. ROW STORE COMPRESS ADVANCED
Answer: D
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 # 31
Users complain about slowness and session interruptions. Additional checks reveal the following error in the application log:
Which file has additional information about this error?
- A. ASH report
- B. Session trace file SQL trace file automatically generated by the error
- C. SQL trace file automatically generated by the error
- D. Alert log
Answer: D
Explanation:
When an ORA-00060 deadlock error occurs, detailed information about the error and the deadlock graph are dumped into the alert log. This log contains a trace file name that you can use to find additional detailed information about the sessions involved in the deadlock and the SQL statements they were executing.
References:
* Oracle Database Administrator's Guide, 19c
* Oracle Database Error Messages, 19c
NEW QUESTION # 32
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