[Q27-Q52] 1z1-084リアル試験問題解答は更新された[2025年04月14日]

1z1-084リアル試験問題解答は更新された[2025年04月14日]

お手軽に合格させる最新Oracle 1z1-084問題集には57問があります

Oracle 1Z0-084試験の準備には、インストラクター主導のトレーニングまたは自己学習があります。Oracleはさまざまなトレーニングコースを提供しており、Performance Tuning in Oracle Database 19c、Oracle Database 19c：SQL Tuning Workshop、Oracle Database 19c：Diagnosing and Tuning SQLなどがあります。さらに、候補者はパフォーマンスとチューニング管理のためのホワイトペーパー、ガイド、ベストプラクティスを含むOracleの公式ドキュメントにアクセスできます。

質問 # 27
Examine this statement and output:

Which two situations can trigger this error?

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

正解：B、C

解説：
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

質問 # 28
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 SQL Patches
B. recommendations regarding rewriting the SQL statements
C. recommendations regarding partitioning the tables
D. recommendations regarding the creation of additional indexes
E. recommendations regarding the creation of materialized views

正解：D、E

解説：
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

質問 # 29
Examine this statement and output:

Which three statements are true?

A. Both 9822 and 8779 sessions are waiting for operating system resources.
B. Session 8779 may be waiting for a user or application response.
C. Session 9857 waited 1354 seconds for another process, which was also waiting for a transaction to end.
D. 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.
E. Session 9857 is not waiting.
F. Session 8779 may be waiting due to a network problem.

正解：B、D、F

解説：
For this SQL statement and output, we can analyze the EVENT column 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

質問 # 30
Examine this statement and output:

Which three statements are true?

A. Both 9822 and 8779 sessions are waiting for operating system resources.
B. Session 8779 may be waiting for a user or application response.
C. Session 9857 waited 1354 seconds for another process, which was also waiting for a transaction to end.
D. 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.
E. Session 9857 is not waiting.
F. Session 8779 may be waiting due to a network problem.

正解：B、D、F

解説：
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

質問 # 31
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 128G, 64G.
B. Disable Automatic Memory Management and set SGA_TARGET to 256G.
C. Set DB_FLASH_CACHE_SIZE parameter to 192G.
D. Set DB_FLASH_CACHE_SIZE to 256G and change device /dev/sdk to 128G.
E. Set DB_FLASH_CACHE_SIZE to 192G and MEMORY_TARGET to 256G.

正解：A

解説：
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 you intend 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

質問 # 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: HW - contention
B. enq: TX - allocate ITL entry
C. enq: TM - contention
D. enq: SQ - contention

正解：A

解説：
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 asession 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

質問 # 33
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 Statspack and import it by using
$ORACLE_HOME/rdbms/admin/awrload into the AWRrepository.
B. 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.
C. 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.
D. Export the data by using expdp from the ftatspack repository and import it by using impdp into the AWR repository.

正解：C

解説：
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

質問 # 34
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 SQL Patches
B. recommendations regarding rewriting the SQL statements
C. recommendations regarding partitioning the tables
D. recommendations regarding the creation of additional indexes
E. recommendations regarding the creation of materialized views

正解：D、E

質問 # 35
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. SQL trace file automatically generated by the error
B. Session trace file SQL trace file automatically generated by the error
C. Alert log
D. ASH report

正解：C

解説：
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

質問 # 36
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 using user-defined virtual column results.
D. It does not improve performance for queries that use join groups on columns from different tables.
E. It can improve OLTP workload performance by avoiding the use of indexes.
F. It improves performance for queries joining several tables using bloom filter joins.

正解：A、E、F

解説：
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

質問 # 37
Examine these commands, which execute successfully:

Which statement is true?

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

正解：D

解説：
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

質問 # 38
Which Optimizer component helps decide whether to use a nested loop join or a hash join in an adaptive execution plan?

A. Dynamic Statistics
B. Statistics Collector
C. SQL Plan Directives
D. Automatic Reoptimization
E. Statistics Feedback

正解：B

解説：
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

質問 # 39
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. Create an index on SALES.TIME_ID to force the return of rows in the order specified by the ORDER BY clause.
B. 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.
C. Replace the FETCH FIRST clause with ROWNUM to enable the use of an index on SALES.
D. Enable Adaptive Plans so that Oracle can change the Join method as well as the Join order for this query.
E. Collect a new set of statistics on PRODUCT, CUSTOMERS, and SALES because the current stats are inaccurate.

正解：A

解説：
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

質問 # 40
Examine this code block, which executes successfully:
DBMS_SERVER_ALERT. SET_THRESHOLD (
DBMS_SERVER_ALERT.CPU_TIME_PER_CALL, DBMS_SERVER_ALERT. OPERATOR_GE, '8000', DBMS_SERVER_ALERT.OPERATOR_GE, '10000', 1, 2, 'inst1', DBMS_SERVER_ALERT.OBJECT_TYPE_SERVICE, 'main.regress.rdbms.dev.us.example.com') ;

What will happen?

A. A warning alert will be issued when CPU time exceeds 1 minute for each user call.
B. A critical alert will be issued when CPU time exceeds 2 minutes for each user call.
C. A warning alert will be issued only when CPU time exceeds 10000 microseconds for each user call.
D. A critical alert will be issued when CPU time exceeds 10000 microseconds for each user call.

正解：D

解説：
In the provided code block, theDBMS_SERVER_ALERT.SET_THRESHOLDprocedure is used to set alert thresholds for the CPU time per call in Oracle Database. This procedure is a part of Oracle's Database Server Alert system, which monitors various metrics and generates alerts when certain thresholds are exceeded.
The parameters passed to theSET_THRESHOLDprocedure are as follows:
* The first parameterDBMS_SERVER_ALERT.CPU_TIME_PER_CALLspecifies the metric for which the threshold is being set, in this case, the CPU time consumed per database call.
* The second and third parametersDBMS_SERVER_ALERT.OPERATOR_GEand'8000'specify the warning threshold level and its value, respectively. However, these are not relevant to the answer as they are overridden by the critical threshold settings.
* The fourth and fifth parametersDBMS_SERVER_ALERT.OPERATOR_GEand'10000'set the critical threshold level and its value. This means that a critical alert will be generated when the CPU time per call exceeds 10000 microseconds.
* The remaining parameters specify the warning and critical alert intervals, the instance name, the object type, and the service name. These are not directly relevant to the behavior described in the options.
Thus, the correct answer is B, as the critical threshold for CPU time per call is set to 10000 microseconds, and the system is configured to issue a critical alert when this threshold is exceeded.
References:
* Oracle Database 19c documentation on theDBMS_SERVER_ALERT.SET_THRESHOLDprocedure, which details the parameters and usage of this procedure for setting alert thresholds within Oracle Database monitoring system.
* Oracle Database Performance Tuning Guide, which provides best practices and methodologies for monitoring and tuning Oracle Database performance, including the use of server alerts and thresholds.

質問 # 41
Which three statements are true about server-generated alerts?

A. Their threshold settings can be modified by using DBMS_SERVER_ALERT.
B. They provide notifications but never any suggestions for correcting the identified problems.
C. They can be viewed only from the Cloud Control Database home page.
D. They may contain suggestions for correcting the identified problems.
E. They are notifications from the Oracle Database Server of an existing or impending problem.
F. They are logged in the alert log.

正解：D、E、F

解説：
Server-generated alerts in Oracle Database are designed to notify DBAs and other administrators about issues within the database environment. These alerts can be triggered by a variety of conditions, including threshold-based metrics and specific events such as ORA- error messages. Here's how these options align with the statements provided:
* A (True):Server-generated alerts are indeed notifications from the Oracle Database Server that highlight existing or impending issues. These alerts are part of Oracle's proactive management capabilities, designed to inform administrators about potential problems before they escalate.
* C (True):These alerts are logged in the alert log of the Oracle Database. The alert log is a crucial diagnostic tool that records major events and changes in the database, including server-generated alerts.
This log is often the first place DBAs look when troubleshooting database issues.
* F (True):Server-generated alerts may include suggestions for correcting identified problems. Oracle Database often provides actionable advice within these alerts to assist in resolving issues more efficiently. These suggestions can range from adjusting configuration parameters to performing specific maintenance tasks.
Options B, D, and E do not accurately describe server-generated alerts:
* B (False):While the statement might have been true in some contexts, Oracle's server-generated alerts often include corrective suggestions, making this statement incorrect.
* D (False):Server-generated alerts can be viewed from various interfaces, not just the Cloud Control Database home page. They are accessible through Enterprise Manager, SQL Developer, and directly within the database alert log, among other tools.
* E (False):While it's true that threshold settings for some alerts can be modified, the method specified, usingDBMS_SERVER_ALERT, is not correct. Threshold settings are typically adjusted through Enterprise Manager or by modifying specific initialization parameters directly.
References:
* Oracle Database Documentation:Oracle Database 19c: Performance Management and Tuning
* Oracle Base: Alert Log and Trace Files
* Oracle Support:Understanding and Managing Server-Generated Alerts

質問 # 42
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: HW - contention
B. enq: TX - allocate ITL entry
C. enq: TM - contention
D. enq: SQ - contention

正解：A

解説：
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

質問 # 43
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 conflict between the two plan stability methods results in an error.
B. The SQL Plan Baseline must be accepted in order to be used for the execution plan.
C. The execution plan is the one enforced by the SQL Profile.
D. The SQL Profiles as well as SQL Plan Baseline are implemented using hints, so they both generate the same plan.
E. The existence of two concurrent plan stability methods generates a child cursor for every execution.
F. The execution plan is the one enforced by the SQL Plan Baseline.

正解：B、C

解説：
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

質問 # 44
You manage a 19c database with default optimizer settings.
This statement is used extensively as subquery in the application queries:
SELECT city_id FROM sh2.sales WHERE city_id=:Bl
You notice the performance of these queries is often poor and, therefore, execute:
SELECT city_id,COUNT(*) FROM sh2.sales GROUP BY city_id;
Examine the results:

There is no index on the CITY_ID column.
Which two options improve the performance?

A. Force the subquery to use dynamic sampling.
B. Generate frequency histograms on the CITY__ID column.
C. Use a SQL Profile to enforce the appropriate plan.
D. Activate the adaptive plans.
E. Create an index on the CITY IP column.

正解：B、E

解説：
In this scenario, creating an index and generating frequency histograms are two methods that can potentially improve performance:
* A (Correct): Generating frequency histograms on the CITY_ID column can help the optimizer make better decisions regarding the execution plan, especially if the data distribution is skewed. Histograms provide the optimizer with more detailed information about the data distribution in a column, which is particularly useful for columns with non-uniform distributions.
* B (Correct): Creating an index on the CITY_ID column would speed up queries that filter on this column, especially if it's used frequently in the WHERE clause as a filter. An index would allow for an index range scan instead of a full table scan, reducing the I/O and time needed to execute such queries.
* C (Incorrect): While SQL profiles can be used to improve the performance of specific SQL statements, they are usually not the first choice for such a problem, and creating a profile does not replace the need for proper indexing or statistics.
* D (Incorrect): Forcing the subquery to use dynamic sampling might not provide a consistent performance benefit, especially if the table statistics are not representative or are outdated. However, dynamic sampling is not as effective as having accurate statistics and a well-chosen index.
* E (Incorrect): Adaptive plans can adjust the execution strategy based on the conditions at runtime.
While they can be useful in certain scenarios, in this case, creating an index and ensuring accurate statistics would likely provide a more significant performance improvement.
References:
* Oracle Database SQL Tuning Guide: Managing Optimizer Statistics
* Oracle Database SQL Tuning Guide: Using Indexes and Clusters

質問 # 45
Examine this statement and its corresponding execution plan:

Which phase introduces the CONCATENATION step?

A. SQL Semantic Check
B. SQL Adaptive Execution
C. SQL Row Source Generation
D. SQL Transformation
E. SQL Execution

正解：D

解説：
The CONCATENATION step in an execution plan is introduced during the SQL Transformation phase. This phase is part of the optimizer's query transformations which can include various techniques to rewrite the query for more efficient execution. The CONCATENATION operation is used to combine the results of two separate SQL operations, typically when there is an OR condition in the WHERE clause, as seen in the provided query.
References:
* Oracle Database SQL Tuning Guide, 19c
* Oracle Database Concepts, 19c

質問 # 46
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 excluding fixed SGA and other internal allocations are readjusted immediately after disabling ASMM.
C. Both SGA_TARGET and SGA_MAX_SIZE must be set to zero.
D. It requires a database instance restart to take effect.
E. The SGA size remains unaffected after disabling ASMM.
F. All SGA components retain their current sizes at the time of disabling.

正解：E、F

解説：
When ASMM is disabled, the sizes of the automatically managed SGA components remain at their current values. ASMM is controlled by theSGA_TARGETparameter. IfSGA_TARGETis 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 settingSGA_TARGETto 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

質問 # 47
What are the least elevated values of statistics_level and C0NTR0LJ4ANAGEMENT_PACK_ACCESS that allow the usage of Monitoring of Database Operations?

A. STATISTICS_LEVEL=ALL and
CONTROL_MANAGEMENT_PACK_ACCESS=DIAGOSTIC+TUNING
B. STATISTICS_LEVEL=TYPICAL and CONTROL_MANAGEMENT_PACK_ACCESS=DIAGOSTIC
C. STATISTICS_LEVEL=TYPICAL and CONTROL_MANAGEMENT_PACK_ACCESS-
DIAGOSTIC*TUNING
D. STATISTICS_LEVEL=BASIC and CONTROL_MANAGEMENT_PACK ACCESS=DIAGOSTIC

正解：A

解説：
Monitoring of Database Operations requires that the STATISTICS_LEVEL parameter be set to ALL and CONTROL_MANAGEMENT_PACK_ACCESS be set to DIAGNOSTIC+TUNING. These settings enable all the advisory features and automatic tuning features within the Oracle Database, including the Automatic Workload Repository (AWR), Automatic Database Diagnostic Monitor (ADDM), and the full functionality of the SQL Tuning Advisor and SQL Access Advisor, which are components of the Diagnostic and Tuning packs.
* STATISTICS_LEVEL=ALL: This setting enables the collection of all system statistics for problem detection and self-tuning purposes.
* CONTROL_MANAGEMENT_PACK_ACCESS=DIAGNOSTIC+TUNING: This grants access to both the Diagnostic Pack and the Tuning Pack, which are essential for detailed performance monitoring and tuning capabilities.
References:
* Oracle Database Reference: STATISTICS_LEVEL
* Oracle Database Licensing Information User Manual: Oracle Database Management Packs

質問 # 48
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. A 99% cache hit ratio can be observed for database instances which have very poor I/O performance.
B. A 60% cache hit ratio can be observed for database instances which have very good I/O performance.
C. The buffer cache advisory view v$db_cache_advice provides advice on cache hit ratios appropriate for the instance workload.
D. Both the RECYCLE and KEEP buffer caches should always have a very high cache hit ratio.
E. The performance of workloads that primarily generate full table scans and fast full index scans are always affected by the cache hit ratio.

正解：A、C

解説：
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

質問 # 49
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 excluding fixed SGA and other internal allocations are readjusted immediately after disabling ASMM.
C. Both SGA_TARGET and SGA_MAX_SIZE must be set to zero.
D. It requires a database instance restart to take effect.
E. The SGA size remains unaffected after disabling ASMM.
F. All SGA components retain their current sizes at the time of disabling.

正解：E、F

解説：
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

質問 # 50
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. In $ORACLE_BASE/diag/rdbms/<db unique name>/<instance name>/trace
B. By viewing V$SERVICE_STATS
C. In the current working directory
D. By viewing V$SERV_MOD_ACT_STATS

正解：D

解説：
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 the V$SERV_MOD_ACT_STATS dynamic 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 (
$ORACLE_BASE/diag), the aggregated statistics for services and modules are not written to trace files but are instead viewable through dynamic performance views.
* C (Incorrect): The V$SERVICE_STATS view 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

質問 # 51
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 128G, 64G.
B. Disable Automatic Memory Management and set SGA_TARGET to 256G.
C. Set DB_FLASH_CACHE_SIZE parameter to 192G.
D. Set DB_FLASH_CACHE_SIZE to 256G and change device /dev/sdk to 128G.
E. Set DB_FLASH_CACHE_SIZE to 192G and MEMORY_TARGET to 256G.

正解：A

解説：
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

質問 # 52
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