[2025年03月] 最新のOracle 1Z0-084認定練習テスト問題 [Q23-Q46]

[2025年03月] 最新のOracle 1Z0-084認定練習テスト問題

確認済み1Z0-084問題集と解答で一年間無料最速更新

質問 # 23
You need to transport performance data from a Standard Edition to an Enterprise Edition database. What is the recommended method to do this?

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

正解：D

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 the exp utility with a parameter file appropriate for Statspack (like spuexp.par) from the Statspack repository and import it into a dedicated Statspack schema on the destination. Since Statspack and AWR use different schemas, it's not recommended to import Statspack data directly into the AWR repository.
The other options are incorrect because:
* A (Incorrect): expdp is not designed to export from Statspack, and awrload is intended for loading from an AWR export file, not a Statspack export.
* B (Incorrect): Although expdp and impdp are used for exporting and importing data, the AWR repository schema is different from the Statspack schema, so importing Statspack data directly into the AWR repository is not recommended.
* C (Incorrect): Using expdp to export from Statspack and then importing directly into the AWR repository is not the correct approach due to the schema differences between Statspack and AWR.
References:
* Oracle Database Performance Tuning Guide: Migrating from Statspack to AWR

質問 # 24
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 performance of workloads that primarily generate full table scans and fast full index scans are always affected by the cache hit ratio.
• B. A 99% cache hit ratio can be observed for database instances which have very poor I/O performance.
• C. A 60% cache hit ratio can be observed for database instances which have very good I/O performance.
• D. The buffer cache advisory view v$db_cache_advice provides advice on cache hit ratios appropriate for the instance workload.
• E. Both the RECYCLE and KEEP buffer caches should always have a very high cache hit ratio.

正解：B、D

質問 # 25
During which application lifecycle phase do you take baselines?

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

正解：C

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

質問 # 26
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: SQ - contention
• D. enq: TM - 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 # 27
Which two types of performance problems are reported by ADDM for PDBS?

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

正解：B、C

解説：
ADDM (Automatic Database Diagnostic Monitor) is a key Oracle diagnostic tool that analyzes performance data captured by AWR (Automatic Workload Repository) and provides insights into performance issues. In a PDB (Pluggable Database), ADDM can provide recommendations for various types of performance issues.
Why A. I/O capacity limits is correct:
* ADDM evaluates the performance of a database and identifies I/O bottlenecks that could be impacting query performance.
* I/O capacity limits occur when the database cannot handle the I/O workload effectively, which could be due to disk contention, inadequate I/O throughput, or hardware limitations.
* ADDM reports such issues and suggests remedies like tuning SQL queries, redistributing I/O workloads, or upgrading storage systems.
Why D. Top SQL statements is correct:
* One of the critical capabilities of ADDM is identifying high-resource-consuming SQL statements (Top SQL) that are impacting database performance.
* For PDBs, ADDM provides specific recommendations to optimize these SQL statements, such as improving execution plans, adding indexes, or rewriting queries.
Why Other Options Are Incorrect:
* B. Excessive checkpoint writes:
* While excessive checkpoint writes can occur, ADDM typically focuses on higher-level performance problems like I/O issues or top SQL rather than specific low-level operational events like checkpointing. Excessive checkpoint writes are not commonly reported directly for PDBs by ADDM.
* C. SGA sizing issues:
* ADDM does not directly analyze or provide recommendations for SGA (System Global Area) sizing issues at the PDB level because SGA is managed at the CDB (Container Database) level.
PDBs share the SGA of the CDB.
* E. User I/O waits:
* While user I/O waits are captured in performance metrics, ADDM typically groups them under broader issues like I/O capacity limits. It does not specifically report on "user I/O waits" as a standalone problem.
Key Features of ADDM for PDBs:
* Identifying Top SQL Statements impacting performance.
* Reporting I/O issues, including capacity limits and contention.
* Highlighting inter-PDB resource contention within the same CDB.
References to Oracle Documentation:
* Oracle Database 19c Performance Tuning Guide:
* Section: Using ADDM for Pluggable Databases.
* Details the types of performance issues ADDM reports for PDBs.
* Automatic Database Diagnostic Monitor (ADDM) Concepts:
* Highlights ADDM's ability to analyze I/O, SQL performance, and resource utilization.

質問 # 28
You need to transport performance data from a Standard Edition to an Enterprise Edition database. What is the recommended method to do this?

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

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 # 29
A database supporting a mixed workload is hosted on a server with 64 CPUs.
A large number of free buffer waits and buffer busy waits occur affecting performance.
The buffer cache size was then increased but after a few hours, the same wait events occur more often than before the change.
Examine these parameter settings:

Which two actions can help reduce the number of these waits7

• A. increasing the value of DBWRITERPROCESSES to 64,
• B. increasing the value of DB_FILE_MULTIBLOCK_READ_COUNT to 128
• C. reducing the values of DB_FILE_MULTILOCK_READ_COUNT to 64
• D. setting dbwr_io_slaves to 64
• E. Increasing the size of MEMORYTARGET

正解：A、D

解説：
Given a server with 64 CPUs, if the buffer cache size increase did not alleviate free buffer waits and buffer busy waits, one can look into optimizing I/O and the efficiency of the DB writer processes.
C: Setting theDBWR_IO_SLAVESparameter to a non-zero value, such as the number of CPUs, would initiate I/O slave processes to assist the DB writer process. This can help reduce I/O contention when writing from the buffer cache to disk, particularly for systems without asynchronous I/O capabilities.
D: Increasing the value ofDBWRITERPROCESSESenables multiple DB writer processes to be active simultaneously. In a system with many CPUs, such as 64, increasing this value can improve the write throughput to disk and potentially reduce buffer busy waits.
References:
* Oracle Database Reference, 19c
* Oracle Database Performance Tuning Guide, 19c

質問 # 30
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. Increase the size of the library cache.
• B. Create the KEEP cache and cache tables accessed by the SQL statements.
• C. Create the RECYCLE cache and cache tables accessed by the SQL statements.
• D. Set the CURSOR_SHARING parameter to FORCE.
• E. Set OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES to TRUE.

正解：A、D

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 the CURSOR_SHARING parameter to FORCE will 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): Setting OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES to TRUE can 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 # 31
Which two statements are true about session wait information contained in v$session or v$session_wait?

• A. Rows for sessions that are not waiting always contain the total wait time since the session started.
• B. Rows for sessions that are currently waiting have a wait time of 0.
• C. Rows for sessions displaying WAITED UNKNOWN TIME in the STATE column indicate that the session is still waiting.
• D. Rows for sessions that are not waiting might contain the actual wait time for the last event for which they waited.
• E. Rows for sessions that are currently waiting have their wait time incremented every microsecond.

正解：B、D

解説：
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

質問 # 32
Examine these statements and output:

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

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

正解：E

解説：
The optimizer_adaptive_statistics parameter, when set to TRUE, enables the optimizer to use adaptive statistics, such as SQL Plan Directives, to help improve plans by automatically adjusting them based on the actual execution statistics.
References:
* Oracle Database SQL Tuning Guide, 19c

質問 # 33
Accessing the SALES tables causes excessive db file sequential read wait events.
Examine this AWR except:

Now, examine these attributes displayed by querying dba_tables:

Finally, examine these parameter settings:

Which two must both be used to reduce these excessive waits?

• A. Compress the SALES table.
• B. Coalesce all sales table indexes.
• C. Partition the SALES table.
• D. Re-create the SALES table.
• E. Increase PCTFREE for the SALES table.

正解：A、C

解説：
The AWR excerpt points to excessive physical reads on the SALES table and index, suggesting the need for optimizing table storage and access.
Partitioning the SALES table (A) can reduce 'db file sequential read' waits by breaking down the large SALES table into smaller, more manageable pieces. This can localize the data and reduce the I/O necessary for query operations.
Compressing the SALES table (D) can also help reduce I/O by minimizing the amount of data that needs to be read from disk. This can also improve cache utilization and reduce the 'db file sequential read' waits.
References:
* Oracle Database VLDB and Partitioning Guide, 19c
* Oracle Database Administrator's Guide, 19c
These changes are recommended based on Oracle's best practices for managing large tables and reducing I/O waits, ensuring better performance and efficiency.

質問 # 34
This error occurred more than four hours ago in the database:
ORA-04036 PGA memory used by the instance exceeds PGA_AGGREGATE_LIMIT
You want to know which process and query were at fault.
Which two views should you use for this purpose?

• A. DBA_HIST_SQLTEXT
• B. DBA_HIST_ACTIVE_SESS_HISTORY
• C. DBA_HIST_PGASTAT
• D. DBA_HIST_PROCESS_MEM_SUMMARY
• E. DBA_HIST_SQLSTAT

正解：B、D

解説：
To investigate the cause of the ORA-04036 error, which indicates that PGA memory usage exceeds the PGA_AGGREGATE_LIMIT, the appropriate views to consult are DBA_HIST_ACTIVE_SESS_HISTORY and DBA_HIST_PROCESS_MEM_SUMMARY.
* DBA_HIST_ACTIVE_SESS_HISTORY: This view provides historical information about active sessions in the database. It includes details about the SQL executed, the execution context, and the resources consumed by each session. By examining this view, you can identify the specific sessions and SQL queries that were active and potentially consuming excessive PGA memory around the time the ORA-04036 error occurred.
* DBA_HIST_PROCESS_MEM_SUMMARY: This view contains historical summaries of memory usage by processes. It can help in identifying the processes that were consuming a significant amount of PGA memory, leading to the ORA-04036 error. This view provides aggregated memory usage information over time, making it easier to pinpoint the processes responsible for high PGA memory consumption.
Together, these views offer a comprehensive overview of the memory usage patterns and specific queries or processes that might have contributed to exceeding the PGA_AGGREGATE_LIMIT, resulting in the ORA-
04036 error.
References:
* Oracle Database Reference: DBA_HIST_ACTIVE_SESS_HISTORY
* Oracle Database Reference: DBA_HIST_PROCESS_MEM_SUMMARY
* Oracle Database Performance Tuning Guide: Managing Memory

質問 # 35
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. Use a SQL Profile to enforce the appropriate plan.
• B. Force the subquery to use dynamic sampling.
• C. Activate the adaptive plans.
• D. Create an index on the CITY IP column.
• E. Generate frequency histograms on the CITY__ID column.

正解：D、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 # 36
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 rewriting the SQL statements
• C. recommendations regarding the creation of additional indexes
• D. recommendations regarding partitioning the tables
• E. recommendations regarding the creation of SQL Patches

正解：A、C

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 # 37
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 performance of workloads that primarily generate full table scans and fast full index scans are always affected by the cache hit ratio.
• B. A 99% cache hit ratio can be observed for database instances which have very poor I/O performance.
• C. A 60% cache hit ratio can be observed for database instances which have very good I/O performance.
• D. The buffer cache advisory view v$db_cache_advice provides advice on cache hit ratios appropriate for the instance workload.
• E. Both the RECYCLE and KEEP buffer caches should always have a very high cache hit ratio.

正解：B、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 # 38
You execute the following:
EXECUTE DBMS_AuTO_TASK_ADMIN.DISABLE;
Which advisor remains enabled?

• A. Automatic Optimizer Statistics Collection
• B. SQL Plan Management Evolve Advisor
• C. Optimizer Statistics Advisor
• D. Automatic SQL Tuning
• E. Automatic Segment Advisor

正解：A

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 # 39
Which three statements are true about tuning dimensions and details of v$sys_time_model and DB time?

• A. Systems in which CPU time is dominant need more tuning that those in which WAIT TIME is dominant.
• B. Parse Time Elapsed accounts for successful soft and hard parse operations only.
• C. When WAIT TIME is high, instance tuning may improve performance.
• D. DB Time accounts for all time used by background processes and user sessions.
• E. The proportion of WAIT TIME to CPU TIME always increases with increased system load.
• F. 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.

正解：C、D、F

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 # 40
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 index IX_SALES_TIME_ID using ADVANCED COMPRESSION.
• B. Re-create the SALES table using the columns in IX_SALES_TIME_ID as the hash partitioning key.
• C. Partition index IX_SALES_TIME_ID using hash partitioning.
• D. Re-create the SALES table sorted in order of index IX_SALES_TIME_ID.

正解：A

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 # 41
Which two options are part of a Soft Parse operation?

• A. Shared Pool Memory Allocation
• B. Syntax Check
• C. Semantic Check
• D. SQL Row Source Generation
• E. SQL Optimization

正解：B、C

解説：
What is a Soft Parse?
A Soft Parse occurs when a SQL statement is already present in the shared SQL area (Shared Pool) of the database. Instead of recreating the execution plan, Oracle reuses the existing plan, making the process much faster and more efficient. This is an essential optimization step in Oracle Database to reduce overhead and improve performance.
Steps Involved in a Soft Parse
* Syntax Check (Step A)
* This is the first step of the parsing process.
* Purpose: Ensures the SQL statement conforms to proper syntax rules defined by the SQL language.
* Example:
SELECT FROM employees;
This query will fail at the Syntax Check step because it doesn't specify any columns to retrieve. Oracle ensures that such malformed queries are identified early.
* Semantic Check (Step E)
* The Semantic Check happens after the Syntax Check if the statement passes the syntax validation.
* Purpose:
* Verify Object Existence: Check if all referenced tables, columns, and other database objects exist. Example:
SELECT salary FROM non_existent_table;
This query will fail because the table non_existent_table does not exist.
* User Privileges: Ensure the user has sufficient permissions to access the objects. Example:
SELECT * FROM employees;
If the user doesn't have SELECT privileges on the employees table, the query will fail.
* Validate Data Types: Ensure that columns used in expressions or comparisons are compatible in terms of data types. Example:
SELECT * FROM employees WHERE hire_date = '01-01-2023';
If hire_date is stored as a DATE type, and the literal is not implicitly convertible, this will fail.
Steps Skipped in a Soft Parse
SQL Row Source Generation (Option B):
This step involves breaking the query into operations (row sources) to fetch data. It is part of execution plan generation, which happens only during a Hard Parse.
SQL Optimization (Option C):
The SQL Optimizer calculates the most efficient execution plan during a hard parse. In a soft parse, the existing plan is reused, so this step is skipped.
Shared Pool Memory Allocation (Option D):
A Hard Parse allocates memory in the shared pool for a new SQL statement. In a soft parse, Oracle reuses the existing shared memory, avoiding additional allocation.
Why Are Syntax Check and Semantic Check the Correct Steps?
These steps are mandatory validations for all SQL statements, even during a soft parse. Without them, Oracle would risk executing invalid or unauthorized SQL statements.
By reusing the execution plan but performing these lightweight checks, Oracle ensures both efficiency and correctness.
References to Oracle Database 19c: Performance Management and Tuning
Oracle Documentation:
Oracle Database 19c Concepts: SQL Parsing and Execution
Oracle Database Performance Tuning Guide: Understanding Hard Parses and Soft Parses Key Features Discussed in the Guide:
Shared Pool and Library Cache: The role of the shared SQL area in reducing parsing overhead.
SQL Execution Workflow: Detailed explanation of syntax and semantic checks.
SQL Optimizer: The differences between hard and soft parsing in relation to the optimizer.
Tools for Analysis:
AWR Reports: Monitor the number of hard vs. soft parses for query performance.
V$SQL: View cached SQL statements and their parsing statistics.

質問 # 42
Which procedure gathers statistics that are always used in the generation of any execution plan?

• A. DBMS_STATS.GATHER_DICTIONARY_STATS
• B. DBMS_STATS.GATHER_DATABASE_STATS
• C. DBMS_STATS.GATHER_SYSTEM_STATS
• D. DBMS_STATS.GATHER_FIXED_ OBJECTS_STATS

正解：B

解説：
TheDBMS_STATS.GATHER_DATABASE_STATSprocedure is used to gather statistics for all schema objects in the database that do not have up-to-date statistics. These statistics are essential for the optimizer to make informed decisions about the most efficient way to execute a query. The procedure collects statistics such as table and column statistics, index statistics, and system statistics, which are all used in the execution plan generation.
References:
* Oracle Database PL/SQL Packages and Types Reference, 19c
* Oracle Database Performance Tuning Guide, 19c

質問 # 43
Which statement is true about DB time in V$$YS_TIME_MODEL?

• A. DB time includes the time spent executing the RMAN backup and restore command.
• B. DB time can be many times greater than the elapsed time since the database instance started.
• C. DB tine excludes the time spent waiting for a CPU in the operating system run queue.
• D. DB time is organized as a simple list of statistics and any time period is attributable to only one statistic.

正解：B

解説：
DB time includes the time spent on user and background processes. It can be greater than the elapsed time because it accumulates the active time of all the processes. For example, if two sessions are each active for 2 seconds at the same time, DB time would accumulate 4 seconds, while the elapsed time would be only 2 seconds.References:
* Oracle Database Performance Tuning Guide, 19c
* Oracle Database Reference, 19c

質問 # 44
Which Optimizer component helps decide whether to use a nested loop join or a hash join in an adaptive execution plan?

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

正解：C

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 # 45
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 rewriting the SQL statements
• C. recommendations regarding the creation of additional indexes
• D. recommendations regarding partitioning the tables
• E. recommendations regarding the creation of SQL Patches

正解：A、C

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 # 46
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Oracle 1Z0-084認定試験は、Oracle Database 19cパフォーマンスとチューニング管理におけるスキルと知識を検証したいITプロフェッショナルにとって貴重な認定試験です。この試験は、パフォーマンスチューニングのコンセプト、ベストプラクティス、ツールの理解をテストするために設計されています。また、データベースのパフォーマンス問題を分析し、最適なチューニングソリューションを提案する能力を検証するためにも設計されています。Oracle 1Z0-084認定試験に合格することは、候補者がOracle Database 19cのパフォーマンスを管理するために必要なスキルと知識を持っていることを示すものです。

 

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