How oracle finds the locatoin of data ?

[Sonia]

hi,

Whenever i issue a query like

sql>select * from emp where empno=25;

How does oracle go about in getting the locations
of the datafile, and segment number in order to retrieve the data.

Which all dictionary table does Oracle need to query
to reach to the table data.

In this scenario what are the roles of the dictionary tables
obj$, fet$, tab$ and seg$.
In which order does oracle query these tables to reach the
exact location of the data ?

regards
sonia

[hrishy]

Hi

well you need to set up tracing for that something like this

create or replace trigger sql_trace after logon on database
begin
if ( user = 'SONIA' )
then
execute immediate 'alter session set events ''10046 trace name context forever, level 12';
end if;
end;

grant alter session to sonia


then login and logout

and
conn as sonia/your_password

select empno from emp where empno=12

then exit

Now go to userdump test and have a look at the trace file you will have everything.

i would have posted the results here but for ora 600 errors i am getting as i need to apply some patches ..

regards
Hrishy