Hotsos Laredo

Laredo has helped us find and fix SQL performance issues before shipping software upgrades to our customers, saving us untold support hours.

—John Schmidt, McKesson Corporation

Why You Need Laredo

With any Oracle application, even small changes made by an application developer or database administrator can make huge differences in application performance.

Some performance changes are particularly insidious; for example, the index you create in January might not ruin performance until December.

Laredo is software that reveals how changes will affect performance, before you make them.

When You Need Laredo

You should never create or drop an index, change an Oracle parameter, or even gather statistics without running Laredo. Laredo helps you find performance differences introduced by changes to any environmental attribute, including:

Schema changes

When you create or drop an index, you change not just the plan for the SQL you're trying to tune, but for potentially dozens of other SQL statements in your application as well. How can you find out which of your 10,000+ SQL statements might perform worse after you create or drop an index?

Oracle parameter changes

More than a dozen parameters influence the behavior of the Oracle cost-based optimizer, including of course sort_area_size, db_file_multiblock_read_count, optimizer_index_cost_adj, and several others. When you alter the value of any of these parameters, you will affect the performance of who knows how many SQL statements. How will you find out which SQL will be affected?

Statistics changes

Anytime you run DBMS_STATS or the old ANALYZE command, you risk changing the execution plans of several of your application's SQL statements. How can you find out which ones, Especially if your application—like many—has more than 10,000+ SQL statements?

Software upgrades

New applications bring new tables, new indexing strategies, and even new SQL. When you upgrade your application, how will you know that you won't introduce regressive performance behavior? New DBMS software releases, or even patches, create the same dilemma. How will you know that a small change in the Oracle query optimizer code won't cause a performance problem somewhere in your application? On the other hand, perhaps you want to test a performance patch before taking it live, to ensure that it will improve your performance as advertised. How can you know it's safe beforehand?

Optimizer technology conversion

Oracle Corporation is phasing out support for its rule-based optimizer (RBO) technology. But moving from rule-based optimization to the Oracle cost-based optimizer (CBO) can lead to unexpected performance problems if you don't catch them in your testing environment.

How It Works

Laredo work flow Laredo has three main components:

Laredo SQL collector

The Laredo SQL collector scours your system for SQL statements, which it stores in a repository. This job is a little more difficult than you might think, especially for applications that do not use bind variables everywhere they should. The Laredo collector has a full-blown SQL parser built in, so it knows when two similar SQL statements should really be considered identical.

Laredo scenario creator

The Laredo scenario creator creates execution plans for a collection of SQL statements in a given environment. The creator stores these execution plans in a repository that makes it easy for you to compare the performance of two scenarios with the Laredo difference reporter.

Laredo difference reporter

The scenario differ reports differences between two Laredo scenarios. For example, if you wanted to know the performance impact of dropping an index, you would create two scenarios for the same SQL collection: one scenario with the index in the environment, and one scenario without the index. The diff of these two scenarios would reveal which parts of your application would have different performance if you were to drop the index.


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The latest release of Laredo can be found on the Hotsos portal. Authorization to download and a logon id are required.

Instructional Videos

There are a few short videos that are helpful to watch before downloading, installing, registering and using Laredo.