with the DBA to discover what the source of some performance issue is, about optimization of SQL queries and PL/SQL scripts, however, you .. Note: You can automatically generate documentation (HTML, PDF, CHM. Oracle Database Performance Tuning Guide, 11g Release 1 () Generating an AWR Report for a SQL Statement on a Specified Database Instance. Director, Database Manageability, Oracle SQL Tuning Solutions – New Feature Overview Writing efficient queries, troubleshooting performance issues .

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DBA's New Best Friend: Advanced SQL Tuning SQL Tuning Advisor, since Oracle Database 10g . There's a lot more to SQL performance than bad plans!. material is subject to the terms and conditions of your Oracle Software License and Tuning SQL. ▫ Preventing Sub-optimal SQL performance: Symptoms. Database performance is one of the most database operations, and SQL tuning can help .. executed under another user ID is probably SQL and PL/. SQL.

Avoid index merges especially if using rule based optimizer Minimize table lookups in queries Join Techniques Sort merge join does not require indexes. Each table is first sorted on the column values used to join the tables and then merges the two sorted result set into one.

Oracle DBA Performance Tuning

Nested loops join Nested loop involves an index on at least one of the table. In this case a full table scan is done on one table.

For every row found a lookup is performed on the second table usually the one which is indexed In a hash join, a hash table is constructed for the larger table. The smaller table is then scanned and the hash table is then used to find matching rows in the larger table Using Join Techniques Use nested loops when only a small subset of the rows needs to be accessed and an index is available to support it. Use sort and hash merge if joining most or all rows of the tables. When determining the best join order try to start with the table which will return the smallest number of rows, providing that the subsequent tables can be joined efficiently.

The optimizer sometimes automatically translates IN-based subqueries into a join. However Oracle has some special optimization for it. Avoid over indexing, specially for columns which are frequently updated. Use array inserts.

Avoid arithmetic calculations in SQL. Perform this work in the program code. Optimizing DML 2 of 4 Retrieve only the columns necessary. SQL Performance Issues: Enables you to test a profile in a restricted environment before making it available to other sessions. Can be enforced at session level or system level. What is SQL Profile?

Workload Tuning: SQL Access Advisor: What could have gone wrong? Case Study 1 My simple query is taking longer than before. How do we approach this problem? Case Study 2 I enabled parallel query. SQL Plan Baselines.

When to use SPA? Test Production Test System: Safe but… Database Database Production System: Optimal Trial Limits testing scope to Mode.

Download Oracle PLSQL Performance Tuning Tips Techniques ebook {PDF} {EPUB}

Knows what change is being tested In-line with routine DBA tasks such as statistics gathering. Find Fix and Validate: Setting to higher values would require higher memory and hence not recommended. SQL Monitor. SQL details. Performance Hub. Historical Performance Hub.

SQL Details. Use Cases. SQL performance is sub. New Features and Enhancements DB AWR Warehouse. SQL Tuning.

Oracle Database In-Memory Advisor: Estimated memory size with various compression options — Benefit: Useful for wide tables. Changes join method from Nested Loops to Hash Join, and vice versa, based on cardinality.

Changes data distribution method among parallel processes from Hybrid Hash to Broadcast, based on cardinality. When SQL statement is executed with statistics feedback monitoring enabled for the first time. Adaptive Statistics — Automatic Reoptimization In contrast to adaptive plans.

After the first execution. If the two values vary significantly then the statement is marked for reoptimization and the initial execution performance statistics are stored as feedback to help compute a more appropriate degree of parallelism for subsequent executions. The parallel degree chosen by the optimizer is compared to the parallel degree computed base on the actual performance statistics e.

CPU-time gathered during the initial execution of the statement. References 2 Day DBA: EM Express Active Reports: EM Express Performance Hub: Performance Tuning - Expert Panel.

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Related titles. Jump to Page. Search inside document. Identify the Blockers and the Objects Causing the Contention Identify the blocking sessions associated with this 5 wait event from the Top Blocking Sessions section Nail down the objects that is subject to this wait 6 from the Top DB Objects Section So how do you resolve this issue?

Ixam Maxi. Abby AR.

Oracle PL/SQL Performance Tuning Tips & Techniques

Bharani Gopi. Aboalfotoh Mahmoud. Jean Jacques Nkuitche Nzokou. Franco Coco Sartori.How do we approach this problem? Table Scans.

Optimize queries based on the query optimization guidelines

Listing 3 shows the output from the plan table shown in Listing 1. Oracle automatic SQL tuning.

The order is not guaranteed. These five steps can be logically thought of as running in sequence — each step starts only after the previous step is completed — although in practice they can be interleaved as long as the final result is not affected.

Analyze ASH:

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