what are host variables in oracle?

What are host variables in oracle
how that increases performances?
Please answer with examples of host variables.
sakthikumarAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

mpaladuguCommented:
see this link...this may be help ful...it also has examples...

http://download.oracle.com/docs/cd/B10500_01/appdev.920/a97269/pc_04dat.htm#27300
0
sdstuberCommented:
host variables do not improve performance by themselves.

however if you write a sql statement like this...


select * from your_table where id = :your_host_variable;


that statement is parsed only once even if you call it with id 1, id 2, id 3, id 4 etc.

but if you do this...


select * from your_table where id = 1;
select * from your_table where id = 2;
select * from your_table where id = 3;
select * from your_table where id = 4;

each of those is 4 distinct sql statements so each must be parsed individually.
parsing is expensive in terms of cpu and requires latching in the SGA.
latching is type of lock,  locks mean you can't scale because they will block other sessions from obtaining the same latch.
So,  failure to bind your host variables into your sql means you will consume more resources than you need to and will inhibit the scalability of your application.


Also note,  if you are using variables for sql from within pl/sql  you get the binding effect automatically.








0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
jiruizCommented:
host variables or bind variables?
0
sdstuberCommented:
bind variables are host variables.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Oracle Database

From novice to tech pro — start learning today.