OERR stands for Oracle Error, which is a utility ships with Oracle distribution for Linux and UNIX that helps retrieve messages from message (.msg) files based on the supplied error code. This utility is not available for Windows, but there are variants freely available on the Internet. The error code consists of two parts, facility …
OERR: The command line Oracle error code lookup utility Read More »
PLAN_TABLE is the default sample output table into which the EXPLAIN PLAN statement inserts rows describing execution plans. This post summarizes the metadata information of this table for Oracle8/8i, 9i, 10g, and 11g; read post, to know the methods for obtaining the formatted explain plan output from plan_table. Column Datatype Description Notes STATEMENT_ID VARCHAR2(30) Value …
Statspack is a set of SQL, PL/SQL and SQL*Plus scripts which allow the collection, automation, storage and viewing of performance data. A user, PERFSTAT, is automatically created by the installation; owns all objects needed by this package. This user is granted limited query-only privileges on the V$views required for performance tuning. A Statspack report is …
Oracle Statistics Package (STATSPACK): A Free Performance Analysis Tool Read More »
The DBMS_PROFILER package provides an interface to profile existing PL/SQL applications and identify performance bottlenecks. You can then collect and persistently store the PL/SQL profiler data. This package enables the collection of profiler (performance) data for performance improvement or for determining code coverage for PL/SQL applications. Application developers can use code coverage data to focus …
How to identify PL/SQL performance bottlenecks using DBMS_PROFILER Read More »
To display the execution plan of all children associated with the SQL ID; you would have to call the table function in below format. Following steps will load two children cursors in the cursor cache By querying V$SQL, We can see that SQL_ID gfvh124qr5nzy has two childrens, 0 and 1; Let us execute DBMS_XPLAN.DISPLAY_CURSOR with …
You can have multiple instances on the same machine, each with their own data files, either sharing the ORACLE_HOME or each with different ORACLE_HOME. ORACLE_HOME and ORACLE_SID are the key environment variables used by Oracle to identify an instance. In addition $ORACLE_HOME/bin must be in your PATH environment variable. To check the value of these …
How to run multiple Oracle database instances on a single server Read More »
To execute any SQL statement Oracle has to derive an ‘execution plan’ . The execution plan of a query is a description of how Oracle will implement the retrieval of data to satisfy a given SQL statement. It is nothing but a tree which contains the order of steps and relationship between them The basic …
You can automatically get a report on the execution path used by the SQL optimizer and the statement execution statistics. The report is generated after successful SQL DML (that is, SELECT, DELETE, UPDATE and INSERT) statements. It is useful for monitoring and tuning the performance of these statements. To use this feature, you must create …
Tuning SQL statements with AUTOTRACE in SQL*Plus Read More »
Methods required to obtain a formatted explain plan differ depending on which version of Oracle you are using. The initial steps to create a plan table and make the optimizer populate the plan table with the execution plan are common to all versions of Oracle. Note that there are limitations with explain plan when the …
Plan Table and methods for obtaining a formatted Explain Plan Read More »
iostat (input/output statistics) an utility that reports Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions. The iostat command is used for monitoring system input/output device loading by observing the time the devices are active in relation to their average transfer rates. The iostat command generates reports that can be used to …
Analyzing Database Server I/O Bottlenecks using IOSTAT Read More »