Leveraging Oracle Database 10g Performance Features in the Real World

Andrew HoldsworthDirector Real World Performance

Server Technologies Oracle Corporation

Session id:40244

Agenda

Oracle9i Feedback Oracle10g Preparation Some Interesting Numbers

Oracle9i Feedback

Over the last year the Real World Performance group has been involved in a large number of performance related projects

– OLTP and Operational Systems– Data Warehouse and DSS Systems– Escalated Customer projects– Proof of Concept Projects– Classic R&D projects

Oracle9i Feedback

We are seeing to much de-tuning of Oracle Databases

– Setting of init.ora parameters to non default values without good reason

– With the exception of init.ora parameters that set buffer sizes the system defaults are usually optimum.

– The impact of excessive “meddling” can be seen in terms of poor optimizer plans, wasted memory, and serialization points.

– In summary let the software run in the manner it was designed to be ran. Don’t try and second guess the software.

Oracle9i Feedback

We are seeing far to many projects that attempt to use new features because they are there and are neglecting design steps.

– Seeing poor data design in terms of table design– Poor index designs– Application design errors resulting in serialization

It is our general rule that an initial design should focus on the relational basics.

Only when the general design is robust and the performance/administration issues are understood should db features be applied e.g. partitioning, parallelism, smart indexes, etc.

Oracle9i Feedback

Top 10 Errors – The documentation of the top 10 errors has

meant that we are seeing these problems less– Looking to review the list for 10g documentation

Oracle9i Feedback

64 Bit Computing misconceptions still exist– 64 Bit systems do not mean they are faster by

definition– 64 Bit systems allow bigger caches and sort

areas– 64 Bit systems have larger working sets and this

impacts CPU efficiency

Oracle9i Feedback

Use of Parallelism and Partitioning for large scale DSS systems is still in the minority

– Not enough parallelism being adopted. Still seeing many serial batch jobs often driven by nested loop queries

– Use of partitioning is mainly for easing database administration issues

– Partitioning should be used for data elimination and enhancing hash joins and parallel dml

Oracle9i Feedback

Much Mismanagement of the CBO– Statistics Abuse common– Expectations often unrealistic– CBO often shows up defects in the data design– Often CBO is being used without anyone

knowing !

Oracle10g Preparation

RBO to CBO Migration should have been done by now

Procrastinate no longer !

Oracle10g Preparation

Some Home Truths about RBO to CBO migration

– It is not a trivial process. Anticipate there will be issues involved in the process

– It only takes one statement to be badly optimized out of 1000s to ruin your day

– Testing and Validation is key to this process

Oracle10g Preparation

– RBO to CBO issues to watch out for Gather good statistics on real data and back them

up Watch out for RBO specific SQL e.g. col+0 = :1 or

col||’’ = :2 Be pragmatic some SQL statements are better

rewritten now Look for Data Skew and Cardinality issues

Oracle10g Preparation

The DUAL table becomes a virtual row source Eliminates the cache buffer chains latch

serialization point Really good for old applications where ‘select

…. From DUAL’ is very common Can be simulated with x$dual in Oracle9i

Oracle10g Preparation

Hash partitioned Indexes– Eliminates the primary key hotspot in insert

heavy applications– Migrates the hot spot to series of warm spots– Very important for RAC or large SMP

implementations

Oracle10g Preparation

Lobs have had considerable code path reduction activity to make performance similar to LONG RAW

Design decisions include– To CACHE or NOCACHE– Storage inline or not– Space usage and wastage– Chunk Size– Logging

Oracle10g Preparation

LOB issues to watch for– Inline to Outline Migration– Cache flooding– OCI LOB Buffering– Use of Array Interface

Oracle10g Preparation

Datapump is an new set of utilities built upon existing direct path and PQ technology.

Allows rapid export/import of datasets Scales like SQL*Loader

– Linear scaling with additional loaders on each CPU

– Caveat the I/O subsystem must be able to keep up !

Oracle10g Preparation

PL/SQL Compiler Improvements Considerable speed up for optimized and non-

optimized compilation of Pl/SQL Applicable for both interpreted and NCOMP

Pl/SQL

Oracle10g Preparation

PL/SQL Compiler Improvements

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5

10

15

20

25

30

9.2 10g(noopt) 10g(opt)

InterpretedNCOMP

Oracle9i to Oracle10g Some Interesting Numbers

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