Is Tuning Obsolete

8/9/2019 Is Tuning Obsolete

1/7


2/7

A Texas Memory Systems PresentationA Texas Memory Systems Presentation

Oracle 9, Tuning DBAs ruled!


Then came Automated temporary tuning

Automated undo segments Automated PGA

Automated SGA

Automated SQL tuning and automatedtotal memory management

Oracle is eliminating tuning from the DBAvocabulary, or are they?


Are Tuning DBAs Cast Out?


Oracle 9-11g Tuning Features

New paths, indexes, structures

Automated Temporary SpaceManagement

Automated UNDO Management

Automated Process Global Area Tuning

Automated SGA Management

Automated SQL Tuning


New Paths, Indexes, Structures Cost based optimization Sort merge join Hash join Star transformation

IOT Bitmap Bitmap join External tables Global temporary tables Partitioning (normal, hash, list) Outlines Profiles


Automated Temporary Space Management

Introduced the temporary tablespace as aseparate entity from a regular tablespace.

Combined with automated segment space

management Sessions sometimes hold on to temporary

segments

Needed a 60+ gigabyte temporary pace for a 18gigabyte data set.

For temporary space management I give Oraclea grade of 3.0 out of 4.0.


3/7


4/7


Automated SGA Management With loads that vary rapidly Oracle would deassign

memory from the shared pool and forget to unlink the list

of SQL areas from the SQL cache, then when a processexecuted that SQL it would go looking in memory basedon the link, not find i t, throw a 7445, then reparse thestatement.

This 7445 error wouldnt stop the instance, it wouldhowever generate a trace and a core dump and thesubsequent filling of the log area would cause hedatabase to halt eventually

I havent seen this problem in the latest releases.


Automated SGA Management

As a good practice, set the old memory

parameters to establish floor values For the automated Memory management I

give Oracle a 3.0


Automatic SQL Tuning

Here there be Monsters!


Automatic SQL Tuning Oracle11g has introduced the concept of automated

tuning. Using a combination of automated jobs, the SQL tuning

advisor, SQL profiles and chutzpah, Oracle now providesautomated SQL tuning

A nightly job kicks off, looks in the AWR and pulls out theheavy hitting SQL and places it in a SQL tuning set.

The SQL tuning set created by the automated job ispassed to SQL Advisor for a comprehensive tuning run

If a profile will give a 300% or greater boost toperformance the profile is activated.

Is SQL Advisor was doing cache flushing as a part of itsdetermination?


Automatic SQL Tuning Manually running the SQL Advisor against a set of 9

TPCH statements, took 30 minutes for the first statementand didnt finish.

A before and after run of the SQLReplay (a new feature

in 11g as well) showed a 50% improvement with no planchanges or addition memory, it was from the affect ofcached data.

SQL advisor in earlier versions had a 60% success ratio

Hesitate to let this run in production until Oracle showsus that they are using on all of their internal databases

I would have to give this new feature a 2.4 out of 4.0.


Other Dumb Oracle Tricks


5/7


Oracle11g Also Offers Execution plan management Statistics management. Used to be

Automated statistics job would run this would invalidate previous SQL plans and they would have to

be reparsed if that resulted in a new execution plan, well, you better hope it

was a better one!

Now Oracle places new statistics in a holding table You give the nod and say yes, those can be published. Oracle will still calculate new execution plans You can turn on a feature that shuttles these new plans off to a

holding table, until you review them.


Statistics and Profile Management

How can these statistics and plans be

reviewed? You could turn them on at the session

level and test in your productionenvironment

Not exactly a good practice


Oracle really wants you to Set up a second server with an Oracle standby

instance

Use various new standby capabilities to halt SQLapply, test using database or SQL replay, thenflashback the entire database and restartstandby.

I dont know but in the last few sentences I think Istumbled against about 5 license landmines

Overall I give these new technologies in Oracleabout a 2.5 out of 4.0

Rather than automating the DBA job, they add tothe grunt work and l icense costs.


So

If you have a database that:

Doesnt have complex SQL

Doesnt have rapidly changing loads

Doesnt have a DBA staff

Turn on the automated tuning and you wil lsee improvements.


But My System is Complex! However:

if you have complex SQL Large load fluctuations A DBA staff

Only implement those features you havecompletely tested and validated under a full loadin a test environment.

Ok.but, I have implemented these andeverything says the database is as tuned as Ican get and still I am not getting theperformance I need, what now?


Physical Tuning

Add disks!

Limited in capability

Still limited to disk latency (5-10milliseconds)

On disk/array caching can help


6/7


7/7


SSD Setup

Usually treated like disks

Set up LUNs and attach to servers Copy files

Use in-place backup plans

Managed like disks


Summary

Dont fire DBAs yet

Overall score for automated options 3.07 Not bad but that is only 75%

However, with:

Good DBA

Auto features

New technology

No excuse for poor performance!


Questions/Comments?


Thank You!

Mike Ault

[email protected]

Is Tuning Obsolete

Documents

Transcript of Is Tuning Obsolete