|Exam Name||:||Oracle Database 11g Release 2- SQL Tuning|
|Questions and Answers||:||125 Q & A|
|Updated On||:||November 21, 2017|
|PDF Download Mirror||:||[1Z0-117 Download Mirror]|
|Get Full Version||:||Pass4sure 1Z0-117 Full Version|
OracleDatabase Data Warehousing Guide,Star Transformation with a Bitmap Index
Which two statements are true about index full scans?
An index fast full scan multi block I/O to read the index structure in its entirely.
Index nodes are not retrieved in the index order, and there fore the nodes are not in sequence.
An index fast full scan reads the index block by block.
An index fast full scan reads the whole index from the lowest value to the higher value.
A:To speed table and index block access, Oracle uses the db_file_multiblock_read_count parameter (which defaults to 8) to aid in getting full-table scan and full-index scan data blocks into the data buffer cache as fast as possible.
B:The index nodes are not retrieved in index order, the rows will not be sequenced.
there are some requirements for Oracle to invoke the fast full-index scan.
index fast full scan tips
An application supplied by a new vendor is being deployed and the SQL statements have plan baselines provided by the supplier. The plans have been loaded from a SQL tuning set. You require the optimizer to use these baselines, but allow better plans to used, should any be created. Which two tasks would you perform to achieve this?
Set the OPTIMIZER_USE_SQL_PLAN_BASELINES initialization parameter to TRUE.
Set the OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES initialization parameter to TRUE.
Use the DBMS_SPM.ALTER_SQL_PLAN_BASELINE function to fix the plans.
Use the DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE function to fix the new plans.
Use the DBMS_SPM.ALTER_SQL_BASELINE function to accept new plans.
A:OPTIMIZER_USE_SQL_PLAN_BASELINES enables or disables the use of SQL plan baselines stored in SQL Management Base. When enabled, the optimizer looks for a SQL plan baseline for the SQL statement being compiled. If one is found in SQL Management B ase, then the optimizer will cost each of the baseline plans and pick one with the lowest cost. D:EVOLVE_SQL_PLAN_BASELINE Function
This function evolves SQL plan baselines associated with one or more SQL statements. A SQL plan baseline is evolved when one or more of its non-accepted plans is changed to an accepted plan or plans. If interrogated by the user (parameter verify = 'YES'), the execution performance of each non-accepted plan is compared against the performance of a plan chosen from the associated SQL plan baseline. If the non-accepted plan performance is found to be better than SQL plan baseline performance, the non-accepted plan is changed to an accepted plan provided such action is permitted by the user (parameter commit = 'YES'). Incorrect:
B:OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES enables or disables the automatic recognition of repeatable SQL statements, as well as the generation of SQL plan baselines for such statements.
This function changes an attribute of a single plan or all plans associated with a SQL statement using the attribute name/value format.
You recently gathered statistics for a table by using the following commands:
You noticed that the performance of queries has degraded after gathering statistics. You want to use the old statistics. The optimizer statistics retention period is default. What must you do to use the old statistics?
Use the flashback to bring back the statistics to the desired time.
Restore statistics from statistics history up to the desired time.
Delete all the statistics collected after the desired time.
Set OPTIMIZER_USE_PENDING_STATISTICS to TRUE.
Whenever statistics in dictionary are modified, old versions of statistics are saved automatically for future restoration. Statistics can be restored using RESTORE procedures of DBMS_STATS package. These procedures use a time stamp as an argument and restore statistics as of that time stamp. This is useful in case newly collected statistics leads to some sub- optimal execution plans and the administrator wants to revert to the previous set of statistics.
Oracle Database Performance Tuning Guide,Restoring Previous Versions of Statistics
View the exhibit and examine the plans in the SQL baseline for a given statement.
Which interpretation is correct?
A new plan cannot be evolved because SYS_SQL_bbedc41f554c408 is accepted.
Plan SYS_SQL_PLAN_bbdc741f554c408 will always be used by the optimizer for the query.
A new plan must be evolved using the DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE function before it can be used.
Plan SYS_SQL_bbedc741a57b5fc2 can be used by the optimizer if the cost of the query is less than plan SYS_SQL_PLAN_bbedc741f554c408.
Plan SYS_SQL_PLAN_bbedc741f554c408 will not be used until it is fixed by using the DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE function.
*Evolving a SQL plan baseline is the process by which the optimizer determines if non-accepted plans in the baseline should be accepted. As mentioned previously, manually loaded plans are automatically marked as accepted, so manual loading forces the evolving process. When plans are loaded automatically, the baselines are evolved using the EVOLVE_SQL_PLAN_BASELINE function, which returns a CLOB reporting its results.
SET LONG 10000
SELECT DBMS_SPM.evolve_sql_plan_baseline(sql_handle => 'SYS_SQL_7b76323ad90440b9') FROM dual;
*Manual plan loading can be used in conjunction with, or as an alternative to automatic plan capture. The load operations are performed using the DBMS_SPM package, which allows SQL plan baselines to be loaded from SQL tuning sets or from specific SQL statements in the cursor cache. Manually loaded statements are flagged as accepted by default. If a SQL plan baseline is present for a SQL statement, the plan is added to the baseline, otherwise a new baseline is created.
*fixed (YES/NO) : If YES, the SQL plan baseline will not evolve over time. Fixed plans are used in preference to non-fixed plans.
You want to run SQL Tuning Advisor statements that are not captured by ADDM, AWR, and are not in the library cache. What is the prerequisite?
Enable SQL plan management
Create a SQL plan baseline for each query
Create a SQL Tuning Set (STS) containing the SQL statements
Gather statistics for objects used in the application
You can use an STS as input to SQL Tuning Advisor, which performs automatic tuning of the SQL statements based on other user-specified input parameters. Note:
A SQL tuning set (STS) is a database object that includes one or more SQL statements along with their execution statistics and execution context, and could include a user priority ranking. You can load SQL statements into a SQL tuning set from different SQL sources, such as AWR, the shared SQL area, or customized SQL provided by the user. An STS includes:
A set of SQL statements
Associated execution context, such as user schema, application module name and action, list of bind values, and the cursor compilation environment
Associated basic execution statistics, such as elapsed time, CPU time, buffer gets, disk reads, rows processed, cursor fetches, the number of executions, the number of complete executions, optimizer cost, and the command type
Associated execution plans and row source statistics for each SQL statement (optional).
OracleDatabase Performance Tuning Guide,Managing SQL Tuning Sets
While tuning a SQL statement, the SQL Tuning Advisor finds an existing SQL profile for a statement that has stale statistics. Automatic optimizer statistics is enabled for the database. What does the optimizer do in this situation?
Updates the existing SQL profiles for which the statistics are stale.
Makes the statistics information available to GATHER_DATABASE_STATS_JOB_PROC
Starts the statistics collection process by running GATHER_STATS_JOB
Writes a warning message in the alert log file
Automatic optimizer statistics collection calls
the DBMS_STATS.GATHER_DATABASE_STATS_JOB_PROC procedure. This internal procedure operates similarly to the DBMS_STATS.GATHER_DATABASE_STATS procedure using the GATHER AUTO option. The main difference is
that GATHER_DATABASE_STATS_JOB_PROCprioritizes database objects that require statistics, so that objects that most need updated statistics are processed first, before the maintenance
window closes. Note:
*The optimizer relies on object statistics to generate execution plans. If these statistics are stale or missing, then the optimizer does not have the necessary information it needs and can generate poor execution plans. The Automatic Tuning Optimizer checks each query object for missing or stale statistics, and produces two types of output:
/Recommendations to gather relevant statistics for objects with stale or no statistics
Because optimizer statistics are automatically collected and refreshed, this problem occurs only when automatic optimizer statistics collection is disabled. See "Managing Automatic Optimizer Statistics Collection".
/Auxiliary statistics for objects with no statistics, and statistic adjustment factor for objects with stale statistics
The database stores this auxiliary information in an object called a SQL profile.
*Oracle recommends that you enable automatic optimizer statistics collection. In this case, the database automatically collects optimizer statistics for tables with absent or stale statistics. If fresh statistics are required for a table, then the database collects them both for the table and associated indexes.
Automatic collection eliminates many manual tasks associated with managing the optimizer. It also significantly reduces the risks of generating poor execution plans because of missing or stale statistics.
Automatic optimizer statistics collection calls the DBMS_STATS.GATHER_DATABASE_STATS_JOB_PROC procedure. This internal procedure operates similarly to the DBMS_STATS.GATHER_DATABASE_STATS procedure using the GATHER AUTO option. The main difference is that GATHER_DATABASE_STATS_JOB_PROC prioritizes database objects that require statistics,so that objects that most need updated statistics are processed first, before the maintenance window closes.
OracleDatabase Performance Tuning Guide,Managing Automatic Optimizer Statistics Collection
Refer to the Exhibit.
What must be the correct order of steps that the optimizer executes based on the ID column the execution plan?
A. 3, 5, 4, 6, 7
B. 3, 5, 4, 7, 6
C. 3, 4, 5, 7, 6
D. 4, 5, 3, 7, 6
Examine the Exhibit.
Which two statements are true about the bloom filter in the execution plan?
The bloom filter prevents all rows from table T1 that do not join T2 from being needlessly distributed.
The bloom filter prevents all rows from table T2 that do not join table T1 from being needlessly distributed.
The bloom filter prevents some rows from table T2 that do not join table T1 from being needlessly distributed.
The bloom filter is created in parallel by the set of parallel execution processes that scanned table T2.
The bloom filter is created in parallel by the set of parallel execution processes that later perform join.
The bloom filter is created in parallel by the set of parallel execution processes that scanned table T1.
PX JOIN FILTER CREATE The bloom filter is created in line 4.
PX JOIN FILTER USE
The bloom filter is used in line 11. Note:
*You can identify a bloom pruning in a plan when you see :BF0000 in the Pstart and Pstop columns of the execution plan and PART JOIN FILTERCREATE in the operations column.
*A Bloom filter is a probabilistic algorithm for doing existence tests in less memory than a full list of keys would require. In other words, a Bloom filter is a method for representing a set of n elements
(also called keys) to support membership queries.
*The Oracle database makes use of Bloom filters in the following 4 situations:
To reduce data communication between slave processes in parallel joins: mostly in RAC
To implement join-filter pruning: in partition pruning, the optimizer analyzes FROM and WHERE
clauses in SQL statements to eliminate unneeded partitions when building the partition access list
To support result caches: when you run a query, Oracle will first see if the results of that query have already been computed and cached by some session or user, and if so, it will retrieve the answer from the server result cache instead of gathering all of the database blocks
To filter members in different cells in Exadata: Exadata performs joins between large tables and small lookup tables, a very common scenario for data warehouses with star schemas. This is implemented using Bloom filters as to determine whether a row is a member of the desired result set.
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The Oracle Certified Expert - SQL Tuning certification has no training requirement or prequisite certification -- if you pass the ">1Z0-117 exam, the expert designation is yours. That said, passing this exam is easier said than done.
">1Z0-117: Oracle Database 11g Release 2: SQL Tuning is an exam in the Oracle Expert series that leads to the “Oracle Database 11g Release 2 SQL Tuning” OCE certification. At this time it is also the newest expert certification to be made available from Oracle Education. Tuning SQL in an Oracle database is both an important and potentially complex task. Creating a new certification for this skill is an excellent move on Oracle’s part and there has been a great deal of interest from the Oracle community in this exam becoming production. The topics on ">1Z0-117 cover the base concepts, techniques, and tools that allow you to detect, diagnose, and resolve problems with poor SQL performance.
Oracle already has a server tuning Expert certification available: Oracle Database 11g Performance Tuning Certified Expert. It requires candidates to either hold a DBA OCP or to take a hands-on training course in addition to passing the exam (1Z0-054). The SQL Tuning expert certification, on the other hand, has no training or certification requirement -- if you pass the ">1Z0-117 exam, the expert designation is yours. That said, passing this exam is easier said than done.
When I took it, the exam had been out of beta for only ten days. This may account for why it felt to me like it still had some of the ‘rough edges’ that I associate with a beta exam. A handful of questions had what I felt were problems with the wording of the question, the answers, or both. I have reported what I could recall of these to Oracle Education. If the exam developers agree that the items I reported were truly flaws, hopefully they will be resolved shortly. On the morning of the test, I really did not need peculiar questions interfering with my concentration. The questions that I understood clearly were strenuous enough.
At 150 minutes, this is the longest non-beta Oracle test I’ve ever taken. You will have almost two full minutes to answer each question and many are complex enough to need that time. A clear majority of the questions that I had were multiple-answer rather than multiple-choice, further increasing the overall difficulty. It is much easier to pick a single right answer than two, three, or four right answers – especially when there is no partial credit.
The test covers a wide range of topics on SQL tuning:
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This Study Guide is targeted at IT professionals who are working towards the OCE certification: Oracle Certified Expert, Oracle Database 11g Release 2 SQL Tuning. The book provides information covering all of the exam topics for the Oracle certification exam: "">1Z0-117: Oracle Database 11g Release 2: SQL Tuning".
The books in the Oracle Certification Prep series are built in lockstep with the test topics provided by Oracle Education's certification program. Each book is intended to provide the information that will be tested in a clean and concise format. The guides introduce the subject you'll be tested on, follow that with the information you'll need to know for it, and then move on to the next topic. They contain no drills or unrealistic self-tests to bump the page count without adding value. The series is intended to provide a concentrated source of exam information that is compact enough to be read through multiple times.
This series is ideal for experienced Oracle professionals that are familiar with the topic being tested, but want a means to rapidly reinforce their existing skills and bridge any gaps in their knowledge. It is also an excellent option as a second source of information for candidates pursuing certification.
Product Details ISBN-13: 9781482775594 : CreateSpace Publishing Publication date: 03292013 Pages: 190 Product dimensions: 6.00(w) x 9.00(h) x 0.40(d) Meet the
Matthew Morris has worked with the Oracle database since 1996 when he worked in the RDBMS support team for Oracle Support Services. Employed by Oracle for over eleven years in support and development positions, Matthew was an early adopter of the Oracle Certified Professional program. He was one of the first one hundred Oracle Certified Database Administrators (version 7.3) and was also in the first hundred to become an Oracle Certified Forms Developer. In the years since, he has upgraded his Database Administrator certification for releases 8i, 9i, 10G and 11G, become an Advanced PLSQL Developer Certified Professional, and added the Expert certifications for Application Express, SQL, and SQL Tuning. Outside of Oracle, he has CompTIA certifications in Linux+ and Security+.
Matthew is an experienced Database Administrator and PLSQL developer and has been creating Web applications with Oracle Application Express since the early days of its release. He is currently employed as a Database Engineer with Computer Sciences Corporation developing enterprise applications.
Article by ArticleForge
Oracle Certification announces the release of the new Oracle Certified Expert, Oracle Database 11g Release 2 SQL Tuning (OCE) certification.
This certification is designed for Developer, DBAs and SQL developers who are proficient at tuning SQL statements. This certification exam covers topics on core elements such as: identifying and tuning inefficient SQL statements, using automatic SQL tuning, managing optimizer statistics on database objects, implementing partitioning and analyzing queries. Up-to-date training and field experience are recommended.
Earning this certification requires passing a single exam: "Oracle Database 11g Release 2: SQL Tuning" (">1Z0-117). This exam recently completed beta testing and is now live for registration through Pearson VUE testing centers worldwide.
Although training is not required for this certification, Oracle University offers several courses to help ensure success on the certification exam:
You can get all preparation details, including exam objectives, number of questions, time allotments, and pricing on the Oracle Certification website.