SQL Server articles, scripts, and discussion groups. SAS/ACCESS(R) 9.2 for Relational Databases: Reference, Fourth Edition Tell us.How satisfied are you with SAS documentation? Thus far in this tips series on Access and SQL Server we have created an ODBC Data Source Name (DSN) using the OLEDB driver, created a System DSN for the new SNAC. ![]() SQLines open source tools can help you transfer data, convert database schema (DDL), stored procedures, functions, packages, triggers, views, queries and SQL scripts.Oracle SQL tuning steps. Oracle Tips by Burleson Consulting. For a complete understanding of SQL tuning. Advanced. Oracle SQL Tuning, a 3- Day or 5- day on- site Oracle course. We also offer a great on site. Oracle tuning training. Tuning individual Oracle SQL statements. The acronym SQL stands for Structured Query. Language. SQL is an industry standard database query language that was. It should not be confused with commercial. Microsoft SQL Server or open source products such as. My. SQL, both of which use the acronym as part of the title of their. There are three major decisions that the SQL. SQL statement: - Access method: Oracle has. Join method: Oracle must decode between nested loops joins, hash join, etc. - Join order: The database has choices about the best table join order. Let's take a closer look at the high level process of SQL tuning: Do this before you start individual. SQL statement tuning. This broad- brush approach can save thousands of hours of. SQL tuning because you can hundreds of queries at once. Remember. MUST do this first, else later changes to the optimizer parameters or. SQL. Remember, you must ALWAYS start with. SQL tuning, else later changes might undo your tuned execution. Optimize the server kernel - You must always tune. I/O subsystem (RAID, DASD bandwidth, network) to. I/O time, network packet size and dispatching frequency. Adjusting your optimizer statistics - You must. Also, histograms can hypercharge SQL in cases of. WHERE clause predicates. Adjust optimizer parameters - Optimizer. Optimize your instance - Your choice of. OS parameters. (db_file_multiblock_read_count, cpu_count, & c), can influence SQL. Tune your SQL Access workload with physical indexes. Just as the SQLAccess advisor recommends. SQL workload with indexes, especially function- based indexes, a Godsend. SQL tuning. 1. 2c Note: The. Oracle 1. 2c SQL Performance Analyzer (SPA), is primarily designed to. SQL tuning process. Once you create a workload (called a SQL Tuning Set, or STS), Oracle. SQL execution plans, based on your environmental. Using SPA, we can predict the impact of system changes on a. SQL after. making any change, like parameter changes, schema changes, hardware. OS changes, or Oracle upgrades. Once the environment, instance, and objects have. Oracle administrator can focus on what is probably the single. Oracle database: tuning the individual SQL. In this final article in my series on Oracle tuning, I will share. SQL statements to improve Oracle. Oracle SQL tuning goals. Oracle SQL tuning is a phenomenally complex subject. Entire books have been. Oracle SQL tuning; however, there are some general. Oracle DBA follows in order to improve the performance of. Again, see the book "Oracle. Tuning: The Definitive Reference", for complete details. The goals of SQL tuning focus on improving the execution plan to fetch the rows. LIO buffer gets and PIO physical. Remove unnecessary large- table full- table scans—Unnecessary full- table scans. I/O and can drag- down an entire database. The tuning expert first evaluates the SQL based on the number of rows. The most common tuning remedy for unnecessary. Standard b- tree indexes can be added to. In some cases, an unnecessary full- table scan can be. SQL statement. Cache small- table full- table scans—In cases where a full- table. In Oracle. 8 and beyond. KEEP pool. Verify optimal index usage—Oracle sometimes has a choice of indexes. Oracle. is using the proper index. Materialize your aggregations and summaries for static. One features of the Oracle. SQLAccess advisor is recommendations for new indexes and suggestions for. Materialized views pre- join tables and. Again, see the book "Oracle. Tuning: The Definitive Reference", for complete details on SQL tuning. These are the goals of SQL tuning in a nutshell. However, they are deceptively. Oracle SQL. Let's begin with an overview of the Oracle SQL. Oracle SQL optimizers. One of the first things the Oracle DBA looks at is the default optimizer. The Oracle initialization parameters offer many. The cost- based optimizer uses. Oracle uses these metrics about the tables in order to. SQL. query. It is important to recognize that in many cases, the cost- based. The cost- based optimizer is constantly being improved. Oracle queries. Prior to Oracle 1. Oracle's default optimizer mode was. In the choose optimizer mode, Oracle will execute the. The danger with using the choose optimizer mode is that problems can. Oracle table in a complex query has. Starting in Oracle 1. The all_rows optimizer mode is designed to minimize computing. Index access. (first_rows_n) adds additional I/O overhead, but they return rows faster. Full- table scans touch all data blocks. Hence, many OLTP shops will choose. Oracle to use indexes to. Index scans return rows fast by doing additional I/O. Note: Staring in Oracle. Oracle performance tuning guide. When only some tables contain. CBO statistics, Oracle will use the cost- based optimization and estimate. This can. cause significant slowdown in the performance of the individual query. In sum, the Oracle database administrator will always try changing the. Oracle tuning. The. Oracle SQL tuning is avoiding the dreaded full- table. One of the hallmarks of an inefficient SQL statement is the. SQL statement to use all of the indexes that are present. Oracle database in order to speed up the query. Of course, there are times when a full- table scan is appropriate for a. Oracle table must be. The task of the SQL tuning expert is to. In most Oracle systems, a SQL statement will be retrieving only a small. The Oracle optimizers are. I/O. However, if the formulation of a query is. Again, the general. Oracle database administrator to interrogate the SQL and. For the full story, see my book "Oracle. Tuning: The Definitive Reference" for details on choosing the right. A strategic plan for. Oracle SQL tuning. Many people ask where they should start when tuning Oracle SQL. Tuning Oracle SQL is like fishing. You must first fish in the. Oracle library cache to extract SQL statements and rank the. Step 1: Identify. SQLThe SQL statements will be ranked according the number of. The executions. column of the v$sqlarea view and the stats$sql_summary or. SQL. Note that we can display SQL statements by: Rows processed: Queries that process a large number. I/O and may also have impact on the. TEMP tablespace. Buffer gets: High buffer gets may indicate a. Disk reads: High disk reads indicate a query that is. I/O. Memory KB: The memory allocation of a SQL statement. CPU secs: This identifies the SQL statements that. Sorts: Sorts can be a huge slowdown, especially if. TEMP tablespace. Executions: The more frequently executed SQL. Step 2: Determine the. SQLAs each SQL statement is identified, it will be. There are a host of. SQL statements. The most common way of determining the execution. SQL statement is to use Oracle's explain plan. By using explain plan, the Oracle DBA can ask Oracle to. SQL statement. To see the output of an explain plan, you must first create a. Oracle provides a script in $ORACLE_HOME/rdbms/admin. Execute utlxplan. Table created. sqlplus > create public synonym plan_table. Synonym created. Most. SQL statement as input, runs the SQL optimizer, and. Listing 1 runs a complex query against a database. EXPLAIN PLAN SET STATEMENT_ID = 'test. FORSET STATEMENT_ID = 'RUN1'INTO plan_table. FORSELECT 'T'||plansnet. P'||detplan. pac. P1', sum(plansnet. FROM plansnet, detplan. WHERE plansnet. AND detplan. pac. N3. 3','1. 92','1. BAI', 'P5. 1','Q2. GROUP BY 'T'||plansnet. P'||detplan. pac. This syntax is piped into the SQL optimizer, which will. RUN1. Please note. The plan. tables contains the following fields: operation: The type of access being. Usually table access, table merge, sort, or. Modifiers to the operation. The name of the table being. Process ID: The identifier for the query. Parent_ID: The parent of the query. Note that several query components may have. Now that the plan_table has been created and populated. Listing 2. plan. sql - displays contents of the explain plan table. SET PAGES 9. 99. 9; SELECT lpad(' ',2*(level- 1))||operation operation, options, object_name, position. FROM plan_table. START WITH id=0. ANDstatement_id = 'RUN1'CONNECT BY prior id = parent_id. ANDstatement_id = 'RUN1'; Listing 3 shows the output from the plan table shown. Listing 1. This is the execution plan for the. SAS/ACCESS(R) 9. 2 for Relational Databases: Reference, Fourth Edition.
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