Publishing Reports to the Web - Downloads - Oracle

Methodology
how the database executes these statements. If you are less proficient in SQL, use the
Data Wizard and Query Builder in the Reports Builder. However, the wizard cannot
prevent inefficient SQL from being created. For example, SQL that does not use
available indexes.
To tune your report's SQL, use the Oracle database's trace functionality. SQL tracing
allows you to determine the SQL statement sent to the database as well as the time
taken to parse, execute, and fetch data. Once a trace file is generated, use the TKPROF
database utility to generate an EXPLAIN PLAN map. The EXPLAIN PLAN map
graphically represents the execution plan used by Oracle Optimizer. For example, the
Oracle Optimizer shows where full table scans have been used. This may prompt you
to create an index on that table depending on the performance hit.
To turn on SQL tracing inside Reports Builder, add a report-level formula column
named SQL_TRACE with the following code:
SRW.DO_SQL(‘ALTER SESSION SET SQL_TRACE=TRUE’);
return(1);
Note: You can also call SQL_TRACE using either a Before Report
Form trigger, or a Before Parameter Form trigger.
The following EXPLAIN PLAN map was generated using the database’s SQL trace
facility. Refer to the SQL Language Reference and Programming documentation for more
information.
Example
The statement being executed is:
SELECT e.ename, d.dname
FROM emp e, dept d
WHERE e.deptno(+) = d.deptno
The EXPLAIN PLAN generated is:
OPERATION OPTIONS OBJECT_NAME POSITION
------------------ ----------- --------------- --------
SELECT STATEMENT
MERGE JOIN OUTER 1
SORT JOIN 1
TABLE ACCESS FULL DEPT 1
SORT JOIN 2
TABLE ACCESS FULL EMP 1
When you tune data for Oracle Reports, understand that the Oracle RDBMS provides
two optimizers: cost-based and rule-based. By default, the cost-based optimizer
constructs an optimal execution plan geared towards throughput, i.e., process all rows
accessed using minimal resources. You can influence the optimizer's choice by setting
the optimizer approach and goal, and gathering statistics for cost-based optimization.
While the cost-based optimizer removes most of the complexity involved in tuning
SQL, understanding the distribution of the data and the optimizer rules allow you to
choose the preferred method and gives you greater control over the execution plan.
For example, in your SQL statement, you could do one of the following:
■ Provide optimizer hints with the goal of best response time, i.e., process the first
row accessed using minimal resources.
■ Decide that an index is not needed.
20-6 Oracle Application Server Reports Services Publishing Reports to the Web