In a multi-processor environment running on an AIX platform, if you are intending to use multi-threaded applications, 

the OS recommendation is to set the environment variable AIXTHREAD_SCOPE=S before invoking this application. 

It results in improved performance of the application.

The syntax to set this variable is:

% export AIXTHREAD_SCOPE=S

Please read more on this . Please note that this is a 3rd party link and is not maintained by Oracle. 

The idea is to help a user gather more information on this and not intended for promotional purposes.

Please also note that setting AIXTHREAD_SCOPE=S is recommended in 

 : Oracle Database (RDBMS) on Unix AIX,HP-UX,Linux,Mac OS X,Solaris,Tru64 Unix Operating Systems Installation and Configuration Requirements Quick Reference (8.0.5 to 11.2)

REFERENCES:ID 458403.1