Written by: Bert
Tuesday, October 02, 2007 9:44 AM 

Often people will write or call to relate that Toad^® seems sluggish when working against Oracle 10g databases – and that creating new connections in particular seems to take an unreasonably long time. They are often especially frustrated since this problem did not occur with Oracle versions prior to 10g. So what is Toad doing that’s wrong (i.e. a bug)?

The short answer is that this is an Oracle 10g DBA best practices issue - and not a Toad problem per se. Toad just happens to expose the symptoms since it makes such frequent access to data dictionary views and tables. The underlying problem generally effects all database applications to a varying degree – it’s just exposed most prominently via Toad.

Oracle versions prior to 10g offered two query optimizers: cost and rule – with rule based being the default and fallback, plus also quite importantly internally used for most access to the data dictionary. While 10g and beyond still offer both optimizers, all access to the data dictionary is via the cost based optimizer, hence the data dictionary needs statistics gathered in order to function efficiently.

The common misconception (and source of the problem) is that people think Oracle 10g does this “auto-magically” as a background task (i.e. GATHER_STATS_JOB). However, the database does not – well not reliably anyway. As a result 90+ percent of the time Toad users experience sluggish performance with 10g, that is the root cause. Most times it takes a “heated debate” between the Toad users, their DBAs, and Quest to convince them to try the quick and very simple fix – which takes just two minutes to perform and then successfully test.

Here’s the Oracle 10g documentation which most times finally gets them to try our fix:

Oracle® Database Performance Tuning Guide
10g Release 2 (10.2)

Chapter: 14 Managing Optimizer Statistics

14.2.3.1 When to Use Manual Statistics

Automatic statistics gathering should be sufficient for most database objects which are being modified at a moderate speed. However, there are cases where automatic statistics gathering may not be adequate…

Another area in which statistics need to be manually gathered are the system statistics. These statistics are not automatically gathered. See "System Statistics" for more information.

Statistics on fixed objects, such as the dynamic performance tables, need to be manually collected using GATHER_FIXED_OBJECTS_STATS procedure.

So here’s the recommended fix (performed via a DBA privileged account):

• exec dbms_stats.gather_dictionary_stats;
• exec dbms_stats.gather_fixed_objects_stats;

These two commands should probably be run about once per week for best results. Of the two commands, the first is far more critical as it handles the “ALL/DBA/USER_*” views and V$ tables – which are accessed constantly from within Toad. The second command is for the X$ tables, which are primarily referenced only by some DBA Module features.

Please consider getting your DBA to make these calls either a scheduled PL/SQL job or possibly implementing them via “on instance start-up” database level trigger.

Now to give you an example of how much difference this process can make – we've clocked screens in Toad (regardless of Toad version) that run quickly on pre-10g, but take very long on a default install of 10g (sometimes as long as 45 minutes). Once the proper data dictionary statistics are collected, Toad performance equals or exceeds the pre-10g timings.

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Tags: toad for oracle , slow , 10g , statistics , speed

Categories: Toad for Oracle

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