[2025年03月] 合格させるOracle 1Z0-084テストエンジンPDFで完全版無料問題集
Oracle Database 19c Performance and Tuning Management練習テスト2025年最新の1Z0-084ストレスなしで合格！
質問 # 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. COLUMN STORE COMPRESS FOR QUERY HIGH
- B. STORE COMPRESS
- C. ROW STORE COMPRESS ADVANCED
- D. MN STORE COMPRESS FOR QUERY LOW
正解：C
解説：
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
質問 # 31
Examine this statement and its corresponding execution plan:
Which phase introduces the CONCATENATION step?
- A. SQL Row Source Generation
- B. SQL Adaptive Execution
- C. SQL Execution
- D. SQL Semantic Check
- E. SQL Transformation
正解：E
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 # 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.
正解：B、C
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 # 33
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;
正解：C
解説：
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
質問 # 34
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 critical alert will be issued when CPU time exceeds 10000 microseconds for each user call.
- B. A warning alert will be issued only when CPU time exceeds 10000 microseconds for each user call.
- C. A critical alert will be issued when CPU time exceeds 2 minutes for each user call.
- D. A warning alert will be issued when CPU time exceeds 1 minute for each user call.
正解：A
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 # 35
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.
正解：B、C
解説：
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
質問 # 36
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.
正解：A、D
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 # 37
SGA_TARGET and PGA_AGGREGATE_TARGET are configured to nonzero values.
MEMORY_target is then set to a nonzero value but memory_MAX_TARGET is not set.
Which two statements are true?
- A.
- B.
- C.
- D.
- E.
- F.
- G.
正解：B、C
解説：
When MEMORY_TARGET is set to a nonzero value, Oracle automatically manages the memory allocation between the System Global Area (SGA) and the Program Global Area(PGA). If MEMORY_MAX_TARGET is not explicitly set, Oracle will behave in the following manner:
* MEMORY_MAX_TARGET will default to the value of MEMORY_TARGET, assuming the platform allows for the value of MEMORY_TARGET to be increased dynamically. This means that MEMORY_TARGET represents both the initial allocation and the maximum limit for the dynamically managed memory unless MEMORY_MAX_TARGET is specified differently.
* If MEMORY_TARGET is set to a value that is less than the sum of the current values of SGA_TARGET and PGA_AGGREGATE_TARGET, Oracle will use the higher sum as the default value for MEMORY_MAX_TARGET to ensure that there is adequate memory for both areas. The database instance will not start if MEMORY_TARGET is not sufficient to accommodate the combined SGA and PGA requirements.
References
* Oracle Database Administrator's Guide 19c: Automatic Memory Management
* Oracle Database Performance Tuning Guide 19c: Using Automatic Memory Management
質問 # 38
Database performance has degraded recently.
index range scan operations on index ix_sales_time_id are slower due to an increase in buffer gets on sales table blocks.
Examine these attributes displayed by querying DBA_TABLES:
Now, examine these attributes displayed by querying DBA_INDEXES:
Which action will reduce the excessive buffer gets?
- A. Re-create the SALES table using the columns in IX_SALES_TIME_ID as the hash partitioning key.
- B. Partition index IX_SALES_TIME_ID using hash partitioning.
- C. Re-create index IX_SALES_TIME_ID using ADVANCED COMPRESSION.
- D. Re-create the SALES table sorted in order of index IX_SALES_TIME_ID.
正解：C
解説：
Given that index range scan operations on IX_SALES_TIME_ID are slower due to an increase in buffer gets, the aim is to improve the efficiency of the index access. In this scenario:
* B (Correct): Re-creating the index using ADVANCED COMPRESSION can reduce the size of the index, which can lead to fewer physical reads (reduced I/O) and buffer gets when the index is accessed, as more of the index can fit into memory.
The other options would not be appropriate because:
* A (Incorrect): Re-creating the SALES table sorted in order of the index might not address the issue of excessive buffer gets. Sorting the table would not improve the efficiency of the index itself.
* C (Incorrect): Using the columns in IX_SALES_TIME_ID as a hash partitioning key for the SALES table is more relevant to data distribution and does not necessarily improve index scan performance.
* D (Incorrect): Hash partitioning the index is generally used to improve the scan performance in a parallel query environment, but it may not reduce the number of buffer gets in a single-threaded query environment.
References:
* Oracle Database SQL Tuning Guide: Managing Indexes
* Oracle Database SQL Tuning Guide: Index Compression
質問 # 39
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 critical alert will be issued when CPU time exceeds 10000 microseconds for each user call.
- B. A warning alert will be issued only when CPU time exceeds 10000 microseconds for each user call.
- C. A critical alert will be issued when CPU time exceeds 2 minutes for each user call.
- D. A warning alert will be issued when CPU time exceeds 1 minute for each user call.
正解：A
解説：
In the provided code block, the DBMS_SERVER_ALERT.SET_THRESHOLD procedure 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 the SET_THRESHOLD procedure are as follows:
* The first parameter DBMS_SERVER_ALERT.CPU_TIME_PER_CALL specifies the metric for which the threshold is being set, in this case, the CPU time consumed per database call.
* The second and third parameters DBMS_SERVER_ALERT.OPERATOR_GE and '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 parameters DBMS_SERVER_ALERT.OPERATOR_GE and '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 the DBMS_SERVER_ALERT.SET_THRESHOLD procedure, 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 # 40
Which three statements are true about server-generated alerts?
- A. They are notifications from the Oracle Database Server of an existing or impending problem.
- B. Their threshold settings can be modified by using DBMS_SERVER_ALERT.
- 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 provide notifications but never any suggestions for correcting the identified problems.
- F. They are logged in the alert log.
正解：A、D、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 # 41
Which three statements are true about tuning dimensions and details of v$sys_time_model and DB time?
- A. DB Time accounts for all time used by background processes and user sessions.
- B. The proportion of WAIT TIME to CPU TIME always increases with increased system load.
- C. Statspack cannot account for high CPU time when CPU TIME is a Top 10 event in DB time. When CPU time is high, SQL tuning may improve performance.
- D. Parse Time Elapsed accounts for successful soft and hard parse operations only.
- E. When WAIT TIME is high, instance tuning may improve performance.
- F. Systems in which CPU time is dominant need more tuning that those in which WAIT TIME is dominant.
正解：A、C、E
解説：
A: Statspack is a performance diagnostic tool that can help identify high CPU usage issues. High CPU time may indicate that SQL statements need to be tuned for better performance.
D: High wait times can often be reduced by instance tuning, such as adjusting database parameters or improving I/O performance.
F: DB Time is a cumulative time metric that includes the time spent by both user sessions and background processes executing database calls.References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Concepts, 19c
質問 # 42
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.
正解：C
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 # 43
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.
正解：C
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 # 44
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. ASH report
- D. Alert log
正解：D
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 # 45
You execute the following:
EXECUTE DBMS_AuTO_TASK_ADMIN.DISABLE;
Which advisor remains enabled?
- A. Optimizer Statistics Advisor
- B. Automatic Optimizer Statistics Collection
- C. SQL Plan Management Evolve Advisor
- D. Automatic SQL Tuning
- E. Automatic Segment Advisor
正解：B
解説：
When you executeDBMS_AUTO_TASK_ADMIN.DISABLE, it disables all automated maintenance tasks related to the Auto Task framework. This includes tasks such as the Automatic SQL Tuning Advisor, Automatic Segment Advisor, and others. However, the Automatic Optimizer Statistics Collection (D) remains enabled as it is not part of the Auto Task framework. The gathering of optimizer statistics is controlled separately and is a critical part of the database's self-tuning mechanism to ensure the optimizer has up-to-date information about the data distribution within tables and indexes.
References
* Oracle Database 19c PL/SQL Packages and Types Reference - DBMS_AUTO_TASK_ADMIN
* Oracle Database 19c Database Administrator's Guide - Managing Optimizer Statistics
質問 # 46
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.
正解：B、D
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 # 47
Database performance has degraded recently.
index range scan operations on index ix_sales_time_id are slower due to an increase in buffer gets on sales table blocks.
Examine these attributes displayed by querying DBA_TABLES:
Now, examine these attributes displayed by querying DBA_INDEXES:
Which action will reduce the excessive buffer gets?
- A. Re-create the SALES table using the columns in IX_SALES_TIME_ID as the hash partitioning key.
- B. Partition index IX_SALES_TIME_ID using hash partitioning.
- C. Re-create index IX_SALES_TIME_ID using ADVANCED COMPRESSION.
- D. Re-create the SALES table sorted in order of index IX_SALES_TIME_ID.
正解：C
解説：
Given that index range scan operations onIX_SALES_TIME_IDare slower due to an increase in buffer gets, the aim is to improve the efficiency of the index access. In this scenario:
* B (Correct):Re-creating the index usingADVANCED COMPRESSIONcan reduce the size of the index, which can lead to fewer physical reads (reduced I/O) and buffer gets when the index is accessed, as more of the index can fit into memory.
The other options would not be appropriate because:
* A (Incorrect):Re-creating theSALEStable sorted in order of the index might not address the issue of excessive buffer gets. Sorting the table would not improve the efficiency of the index itself.
* C (Incorrect):Using the columns inIX_SALES_TIME_IDas a hash partitioning key for theSALES table is more relevant to data distribution and does not necessarily improve index scan performance.
* D (Incorrect):Hash partitioning the index is generally used to improve the scan performance in a parallel query environment, but it may not reduce the number of buffer gets in a single-threaded query environment.
References:
* Oracle Database SQL Tuning Guide:Managing Indexes
* Oracle Database SQL Tuning Guide:Index Compression
質問 # 48
Which two statements are true about space usage in temporary tablespaces?
- A. Lack of temporary tablespace space for sort operations can be prevented by using temporary tablespace groups.
- B. A sort will fail if a sort to disk requires more disk space and no additional extent can be found/allocated in/for the sort segment.
- C. When a global temporary table instantiation is too large to fit in memory, space is allocated in a temporary tablespace.
- D. When a session consumes all temporary tablespace storage, then the session would hang until the temporary space used by that session is cleared.
- E. Temporary tablespaces setting Includes quotas to limit temporary space used by a session for that Temporary tablespace.
正解：A、C
解説：
Regarding space usage in temporary tablespaces, the following statements are true:
* A (Correct): When a global temporary table or a sort operation exceeds the available memory, Oracle Database allocates space in a temporary tablespace to store the temporary data or intermediate results.
* E (Correct): Using temporary tablespace groups can prevent insufficient temporary tablespace for sort operations by providing a collective pool of space from multiple temporary tablespaces, which can be used for user sorting operations.
The other options provided have inaccuracies:
* B (Incorrect): Oracle does not provide a mechanism for setting quotas on temporary tablespaces.
Quotas can be set for permanent tablespaces but not for temporary ones.
* C (Incorrect): A sort operation may fail due to insufficient space, but Oracle will attempt to allocate space in the temporary tablespace dynamically. If no space can be allocated, an error is returned rather than a sort failure.
* D (Incorrect): If a session consumes all available temporary tablespace storage, Oracle will not hang the session; it will return an error to the session indicating that it has run out of temporary space.
References:
* Oracle Database Administrator's Guide: Managing Space for Schema Objects
* Oracle Database Concepts: Temporary Tablespaces
質問 # 49
......
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