1Z0-084指南：Oracle Database 19c Performance and Tuning Management考試通過證明

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最新的 Oracle Database 19c 1Z0-084 免費考試真題 (Q56-Q61):

問題 #56
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. Partition the SALES table.
B. Increase PCTFREE for the SALES table.
C. Compress the SALES table.
D. Re-create the SALES table.
E. Coalesce all sales table indexes.

答案：A,C

解題說明：
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.

問題 #57
Which two statements are true about Data Pump import for objects that used the in Memory (IM) column store in their source database?

A. Its INMEM0RY_CLAUSE of the Data Pump Export allows modifications to IM column store clause of a table with existing INMEMORY setting.
B. It always gives preference to the IM column store clause defined at the tablespace level over table-level definitions.
C. Its TRANSFORM clause can be used to add the INMEMORV clause to exported tables that lack them.
D. It can generates the INMEMORY clause that matches the table settings at export time.
E. It must always transports existing INMEMORY attributes.
F. It ignores the IM column store clause of the exporting objects.

答案：C,D

解題說明：
When importing objects that used the In-Memory (IM) column store in their source database using Oracle Data Pump, the following statements are true:
* D (Correct):TheTRANSFORMclause can be used to alter object creation DDL during import operations. This can include adding theINMEMORYclause to tables that were not originally using the IM column store.
* F (Correct):The import operation can preserve theINMEMORYattributes of tables as they were at the time of export, effectively replicating the IM column store settings from the source database.
The other statements are not accurate in the context of Data Pump import:
* A (Incorrect):Data Pump does not give preference to the IM column store clauses at the tablespace level over table-level definitions unless explicitly specified by theTRANSFORMclause.
* B (Incorrect):While Data Pump can transport existingINMEMORYattributes, it is not mandatory. It is controlled by theINCLUDEorEXCLUDEData Pump parameters or theTRANSFORMclause.
* C (Incorrect):TheINMEMORY_CLAUSEparameter is not part of the Data Pump Export utility. To modify the IM column store clauses, you would use theTRANSFORMparameter during import, not export.
* E (Incorrect):Data Pump does not ignore the IM column store clause unless specifically instructed to do so via theEXCLUDEparameter.
References:
* Oracle Database Utilities:Data Pump Export
* Oracle Database Utilities:Data Pump Import

問題 #58
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 execution plan is the one enforced by the SQL Plan Baseline.
C. The existence of two concurrent plan stability methods generates a child cursor for every execution.
D. The SQL Plan Baseline must be accepted in order to be used for the execution plan.
E. The execution plan is the one enforced by the SQL Profile.
F. The SQL Profiles as well as SQL Plan Baseline are implemented using hints, so they both generate the same plan.

答案：D,E

解題說明：
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

問題 #59
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. Both the RECYCLE and KEEP buffer caches should always have a very high cache hit ratio.
B. A 99% cache hit ratio can be observed for database instances which have very poor 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. A 60% cache hit ratio can be observed for database instances which have very good I/O performance.
E. The performance of workloads that primarily generate full table scans and fast full index scans are always affected by the cache hit ratio.

答案：B,C

解題說明：
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

問題 #60
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. Both the RECYCLE and KEEP buffer caches should always have a very high cache hit ratio.
B. A 99% cache hit ratio can be observed for database instances which have very poor 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. A 60% cache hit ratio can be observed for database instances which have very good I/O performance.
E. The performance of workloads that primarily generate full table scans and fast full index scans are always affected by the cache hit ratio.

答案：B,C

解題說明：
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

問題 #61
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最新1Z0-084題庫資源: https://www.vcesoft.com/1Z0-084-pdf.html