DBA's New Best Friend: Advanced SQL Tuning. Features of Oracle Database 11g. Peter Belknap, Sergey Koltakov, Jack Raitto. Oracle Database SQL Tuning Guide, 12c Release 2 () AMD logo, and the AMD Opteron logo are trademarks or registered trademarks of Advanced Micro. SQL Tuning for Smarties, Dummies and Everyone in Between. Novices SQL Tuning Solutions – New Feature Overview. • Problem .. Advanced SQL Tuning.
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Jul 14, Oracle Database SQL Tuning Guide, 12c Release 1 () AMD Opteron logo are trademarks or registered trademarks of Advanced Micro. Sep 21, about optimization of SQL queries and PL/SQL scripts, however, you have to understand the basics of SQL. advanced optimization techniques. .. Note: You can automatically generate documentation (HTML, PDF, CHM. more efficient forms and the use of advanced techniques such as devoted to the nuances of Oracle SQL tuning, most notably the Kimberly Floss book.
Simple, huh? This is exactly why the Cost Based Optimizer exists. Unfortunately Oracle s Cost Based Optimization process is not perfect; in some cases because of the Optimizer s design limitations, sometimes bugs, but often because incorrectly configured optimizer environment and statistics collection setup.
This part of the seminar provides you the required understanding of CBO internals and SQL plan execution s cost estimation process. Armed with this knowledge you will learn how to put together a strategy for configuring Cost Based Optimizer environment and statistics collection correctly. We will look into different requirements by different workloads such as OLTP vs.
All of these APIs have built-in support for bind variables. ADO in the case of VB. Bind Variables in VB. JDBC in the case of Java. Java has PreparedStatement.
CPU time. Note that statistics can be either computed or estimated. The smallest amount of data read is a single Oracle block. How does Oracle access data? Most frequently seen in explain plans as Table access by Rowid. If you have deleted all the rows then you will still read up to the HWM. Data is accessed by looking up key values in an index and returning rowids. Truncate resets the HWM back to the start of the table.
A rowid uniquely identifies an individual row in a particular data block. This is the quickest access method available Oracle simply retrieves the block specified and extracts the rows it is interested in. In a FTS operation. The HWM marks the last block in the table that has ever had data written to it. Oracle will analyze the statement and fill a special table with the Execution plan for that statement.
This is explained below. If all the required data resides in the index then a table lookup may be unnecessary and all you will see is an index access with no table access.
This indicates that the table data is not being accessed via a FTS operation but rather by a rowid lookup. In this case the rowid has been produced by looking up values in the index first. Notice that no table access takes place: Method for looking up a single key value via a unique index. In certain circumstances it is possible for the whole index to be scanned as opposed to a range scan.
Rows are not returned in sorted order. Scans all the block in the index. Like a non-unique index.
Oracle compares each row of the outer set with each row of the inner set and returns those rows that satisfy a condition. An operation that accepts two sets of rows. VIEW An operation that performs a view's query and then returns the resulting rows to another operation.
Do the Work by Steven Pressfield
MINUS An operation that accepts two sets of rows and returns rows that appear in the first set but not in the second. The query optimizer operates in two modes: SQL Profiling iii. Under normal mode. The output of this type of analysis is a recommendation to accept the SQL Profile. The Automatic Tuning Optimizer checks each query object for missing or stale statistics.
If such an index is identified. If these statistics are stale or missing.
If accepted. The query optimizer relies on object statistics to generate execution plans. The normal mode of the optimizer generates a reasonable execution plan for the vast majority of SQL statements.
In normal mode. Indexes can tremendously enhance performance of a SQL statement by reducing the need for full table scans on large tables.
A SQL Profile. The Automatic Tuning Optimizer performs four types of tuning analysis : The query optimizer can sometimes produce inaccurate estimates about an attribute of a statement due to lack of information. The additional overhead of running the SQL Trace facility against an application with performance problems is normally insignificant compared with the inherent overhead caused by the application's inefficiency.
When running in the tuning mode. Access Path Analysis iv. Statistics Analysis ii. Because the Automatic Tuning Optimizer does not analyze how its index recommendation can affect the entire SQL workload. The Automatic Tuning Optimizer also explores whether a new index can significantly enhance the performance of a query.
Because optimizer statistics are automatically collected and refreshed. A special feature in 11g  is that when SQL statements are executed by the Oracle database. This auxiliary information is stored in an object called a SQL Profile. The output of the query optimizer is not an execution plan. We can enable the SQL Trace facility for a session or for an instance. Mary Jacintha HOD. For instance. These changes require a good understanding of the data properties and should be implemented only after careful consideration.
Nov 3. Query optimization is the refining process in database administration and it helps to bring down speed of execution. Attributes can be customized for the maintenance of windows. An application developer can then determine if the advice is applicable to their situation or not.
Advanced SQL Tuning Features of Oracle Database 11g
Sergey Koltakov. Jack Raitto. The Automatic Tuning Optimizer identifies common problems with structure of SQL statements that can lead to poor performance. The recommendation relates to collection of statistics on objects.
Types of SQL Statements
These could be syntactic. You can choose to accept the recommendation to complete the tuning of the SQL statements. It is always a collective task that is rewarded. This tool hence provides an edge over the other tools as it leads to faster processing of the query.Search inside document. If we use services with our database. The recommendation relates to collection of statistics on objects, creation of new indexes, restructuring of the SQL statement, or creation of a SQL profile.
Because optimizer statistics are automatically collected and refreshed, this problem may be encountered only when automatic optimizer statistics collection has been turned off. It also involved one of the major disadvantages of involving several manual steps.
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