Exam Code: 1Z0-062 (Practice Exam Latest Test Questions VCE PDF)
Exam Name: Oracle Database 12c: Installation and Administration
Certification Provider: Oracle
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2021 Feb 1Z0-062 practice test
Q1. Which three statements are true about adaptive SQL plan management?
A. It automatically performs verification or evolves non-accepted plans, in COMPREHENSIVE mode when they perform better than existing accepted plans.
B. The optimizer always uses the fixed plan, if the fixed plan exists in the plan baseline.
C. It adds new, bettor plans automatically as fixed plans to the baseline.
D. The non-accepted plans are automatically accepted and become usable by the optimizer if they perform better than the existing accepted plans.
E. The non-accepted plans in a SQL plan baseline are automatically evolved, in COMPREHENSIVE mode, during the nightly maintenance window and a persistent verification report is generated.
Answer: A,D,E
Explanation: With adaptive SQL plan management, DBAs no longer have to manually run the verification or evolve process for non-accepted plans. When automatic SQL tuning is in COMPREHENSIVE mode, it runs a verification or evolve process for all SQL statements that have non-accepted plans during the nightly maintenance window. If the non-accepted plan performs better than the existing accepted plan (or plans) in the SQL plan baseline, then the plan is automatically accepted and becomes usable by the optimizer. After the verification is complete, a persistent report is generated detailing how the non-accepted plan performs compared to the accepted plan performance. Because the evolve process is now an AUTOTASK, DBAs can also schedule their own evolve job at end time.
Note:
* The optimizer is able to adapt plans on the fly by predetermining multiple subplans for portions of the plan.
* Adaptive plans, introduced in Oracle Database 12c, enable the optimizer to defer the final plan decision for a statement until execution time. The optimizer instruments its chosen plan (the default plan) with statistics collectors so that it can detect at runtime, if its cardinality estimates differ greatly from the actual number of rows seen by the operations in the plan. If there is a significant difference, then the plan or a portion of it will be automatically adapted to avoid suboptimal performance on the first execution of a SQL statement.
Reference: SQL Plan Management with Oracle Database 12c
Q2. Which two statements are true about Oracle Managed Files (OMF)?
A. OMF cannot be used in a database that already has data files created with user-specified directions.
B. The file system directions that are specified by OMF parameters are created automatically.
C. OMF can be used with ASM disk groups, as well as with raw devices, for better file management.
D. OMF automatically creates unique file names for table spaces and control files.
E. OMF may affect the location of the redo log files and archived log files.
Answer: D,E
Explanation:
D: The database internally uses standard file system interfaces to create and delete files as needed for the following database structures:
Tablespaces Redo log files Control files Archived logs Block change tracking files Flashback logs RMAN backups
Note:
* Using Oracle-managed files simplifies the administration of an Oracle Database. Oracle-managed files eliminate the need for you, the DBA, to directly manage the operating system files that make up an Oracle Database. With Oracle-managed files, you specify file system directories in which the database automatically creates, names, and manages files at the database object level. For example, you need only specify that you want to create a tablespace; you do not need to specify the name and path of the tablespace's datafile with the DATAFILE clause.
http://www.oracle-base.com/articles/9i/oracle-managed-files.php http://docs.oracle.com/cd/B10500_01/server.920/a96521/omf.htm Reference: What Are Oracle-Managed Files?
Q3. Examine the following command;
ALTER SYSTEM SET enable_ddl_logging = TRUE;
Which statement is true?
A. Only the data definition language (DDL) commands that resulted in errors are logged in the alert log file.
B. All DDL commands are logged in the alert log file.
C. All DDL commands are logged in a different log file that contains DDL statements and their execution dates.
D. Only DDL commands that resulted in the creation of new segments are logged.
E. All DDL commands are logged in XML format in the alert directory under the Automatic Diagnostic Repository (ADR) home.
Answer: B
Explanation: Once DDL logging is turned on, every DDL command will be logged in the alert log file and also the log.xml file.
Note:
* By default Oracle database does not log any DDL operations performed by any user. The default settings for auditing only logs DML operations.
* Oracle 12c DDL Logging – ENABLE_DDL_LOGGING
The first method is by using the enabling a DDL logging feature built into the database. By default it is turned off and you can turn it on by setting the value of ENABLE_DDL_LOGGING initialization parameter to true.
* We can turn it on using the following command. The parameter is dynamic and you can
turn it on/off on the go.
SQL> alter system set ENABLE_DDL_LOGGING=true;
System altered. Elapsed: 00:00:00.05 SQL>
Once it is turned on, every DDL command will be logged in the alert log file and also the log.xml file.
Q4. Which two statements correctly describe the relationship between data files and logical database structures?
A. A segment cannot span data files.
B. A data file can belong to only one tablespace.
C. An extent cannot span data files.
D. The size of an Oracle data block in a data file should be the same as the size of an OS block.
Answer: B,C
Reference: https://mohibalvi.wordpress.com/tag/alter-tablespace/
Q5. Which three statements are true about Automatic Workload Repository (AWR)?
A. All AWR tables belong to the SYSTEM schema.
B. The AWR data is stored in memory and in the database.
C. The snapshots collected by AWR are used by the self-tuning components in the database
D. AWR computes time model statistics based on time usage for activities, which are displayed in the v$SYS time model and V$SESS_TIME_MODEL views.
E. AWR contains system wide tracing and logging information.
Answer: B,C,E
Explanation: * A fundamental aspect of the workload repository is that it collects and persists database performance data in a manner that enables historical performance analysis. The mechanism for this is the AWR snapshot. On a periodic basis, AWR takes a “snapshot” of the current statistic values stored in the database instance’s memory and persists them to its tables residing in the SYSAUX tablespace.
* AWR is primarily designed to provide input to higherlevel components such as automatic tuning algorithms and advisors, but can also provide a wealth of information for the manual tuning process.
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Q6. You are about to plug a multi-terabyte non-CDB into an existing multitenant container database (CDB).
The characteristics of the non-CDB are as follows:
Version: Oracle Database 11g Release 2 (11.2.0.2.0) 64-bit Character set: AL32UTF8 National character set: AL16UTF16 O/S: Oracle Linux 6 64-bit
The characteristics of the CDB are as follows:
Version: Oracle Database 12c Release 1 64-bit Character Set: AL32UTF8 National character set: AL16UTF16 O/S: Oracle Linux 6 64-bit
Which technique should you use to minimize down time while plugging this non-CDB into the CDB?
A. Transportable database
B. Transportable tablespace
C. Data Pump full export/import
D. The DBMS_PDB package
E. RMAN
Answer: B
Explanation: * Overview, example:
-Log into ncdb12c as sys
-Get the database in a consistent state by shutting it down cleanly.
-Open the database in read only mode
-Run DBMS_PDB.DESCRIBE to create an XML file describing the database.
-Shut down ncdb12c
-Connect to target CDB (CDB2)
-Check whether non-cdb (NCDB12c) can be plugged into CDB(CDB2)
-Plug-in Non-CDB (NCDB12c) as PDB(NCDB12c) into target CDB(CDB2).
-Access the PDB and run the noncdb_to_pdb.sql script.
-Open the new PDB in read/write mode.
* You can easily plug an Oracle Database 12c non-CDB into a CDB. Just create a PDB manifest file for the non-CDB, and then use the manifest file to create a cloned PDB in the CDB.
* Note that to plugin a non-CDB database into a CDB, the non-CDB database needs to be of version 12c as well. So existing 11g databases will need to be upgraded to 12c before they can be part of a 12c CDB.
Q7. Examine the parameter for your database instance:
You generated the execution plan for the following query in the plan table and noticed that the nested loop join was done. After actual execution of the query, you notice that the hash join was done in the execution plan:
Identify the reason why the optimizer chose different execution plans.
A. The optimizer used a dynamic plan for the query.
B. The optimizer chose different plans because automatic dynamic sampling was enabled.
C. The optimizer used re-optimization cardinality feedback for the query.
D. The optimizer chose different plan because extended statistics were created for the columns used.
Answer: B
Explanation: * optimizer_dynamic_sampling OPTIMIZER_DYNAMIC_SAMPLING controls both when the database gathers dynamic statistics, and the size of the sample that the optimizer uses to gather the statistics. Range of values0 to 11
Q8. You notice a performance change in your production Oracle database and you want to know which change has made this performance difference.
You generate the Compare Period Automatic Database Diagnostic Monitor (ADDM) report to further investigation.
Which three findings would you get from the report?
A. It detects any configuration change that caused a performance difference in both time periods.
B. It identifies any workload change that caused a performance difference in both time periods.
C. It detects the top wait events causing performance degradation.
D. It shows the resource usage for CPU, memory, and I/O in both time periods.
E. It shows the difference in the size of memory pools in both time periods.
F. It gives information about statistics collection in both time periods.
Answer: A,B,D
Explanation: Keyword: shows the difference.
* Full ADDM analysis across two AWR snapshot periods Detects causes, measure effects, then correlates them Causes: workload changes, configuration changes Effects: regressed SQL, reach resource limits (CPU, I/O, memory, interconnect) Makes actionable recommendations along with quantified impact
* Identify what changed / Configuration changes, workload changes
* Performance degradation of the database occurs when your database was performing optimally in the past, such as 6 months ago, but has gradually degraded to a point where it becomes noticeable to the users. The Automatic Workload Repository (AWR) Compare Periods report enables you to compare database performance between two periods of time.
While an AWR report shows AWR data between two snapshots (or two points in time), the AWR Compare Periods report shows the difference (ABE) between two periods (or two AWR reports with a total of four snapshots). Using the AWR Compare Periods report helps you to identify detailed performance attributes and configuration settings that differ between two time periods.
Reference: Resolving Performance Degradation Over Time
Q9. Which two statements are true about the Oracle Direct Network File system (DNFS)?
A. It utilizes the OS file system cache.
B. A traditional NFS mount is not required when using Direct NFS.
C. Oracle Disk Manager can manage NFS on its own, without using the operating kernel NFS driver.
D. Direct NFS is available only in UNIX platforms.
E. Direct NFS can load-balance I/O traffic across multiple network adapters.
Answer: C,E
Explanation: E: Performance is improved by load balancing across multiple network interfaces (if available).
Note:
* To enable Direct NFS Client, you must replace the standard Oracle Disk Manager (ODM) library with one that supports Direct NFS Client.
Incorrect: Not A: Direct NFS Client is capable of performing concurrent direct I/O, which bypasses any operating system level caches and eliminates any operating system write-ordering locks Not B:
* To use Direct NFS Client, the NFS file systems must first be mounted and available over regular NFS mounts.
* Oracle Direct NFS (dNFS) is an optimized NFS (Network File System) client that provides faster and more scalable access to NFS storage located on NAS storage devices (accessible over TCP/IP). Not D: Direct NFS is provided as part of the database kernel, and is thus available on all supported database platforms - even those that don't support NFS natively, like Windows.
Note:
* Oracle Direct NFS (dNFS) is an optimized NFS (Network File System) client that provides faster and more scalable access to NFS storage located on NAS storage devices (accessible over TCP/IP). Direct NFS is built directly into the database kernel - just like ASM which is mainly used when using DAS or SAN storage.
* Oracle Direct NFS (dNFS) is an internal I/O layer that provides faster access to large NFS files than traditional NFS clients.
Q10. Examine the resources consumed by a database instance whose current Resource Manager plan is displayed.
SQL> SELECT name, active_sessions, queue_length, Consumed_cpu_time, cpu_waits, cpu_wait_time
FROM v$rsrc_consumer_group;
NAMEACTIVE_SESSIONS QUEUE_LENGTH CONSUMED_CPU_WAITS
CPU_WAIT_TIME
OLTP__ORDER__ENTRY1029690 467
OTHES__GROUPS 0 059823664089
60425
SYS_GROUP 1 02420704 914
19540
DS.S_QUERIES4245946603004
55700
Which two statements are true?
A. An attempt to start a new session by a user belonging to DSS_QUERIES fails with an error.
B. An attempt to start a new session by a user belonging to OTHE_GROUPS fails with an error.
C. The CPU_WAIT_TIME column indicates the total time that sessions in the consumer group waited for the CPU due to resource management.
D. The CPU_WAIT_TIME column indicates the total time that sessions in the consumer group waited for the CPU due to I/O waits and latch or enqueue contention.
E. A user belonging to the DSS__QUERIES resource consumer group can create a new session but the session will be queued.
Answer: C,E