To understand OLS you could read oracle documentation about it, OLS has two parts One binary which installed through Oracle Universal Installer (OUI) and to know if you have been install it you can check log in information to sqlplus banner
Oracle Label Security ….
All this in the 11g become more easier since you can install all features while you choose enterprise edition and use chopt to enable and disable :
chopt enable lbac
chopt disable lbac
talking about second part which can be installed via PL/SQL packages,all this can be installed thru catols.sql
and you can use this way in 10g or 11g, and to de-install the OLS you can use the catnools.sql. but just as information oracle recommend that to install OLS you need to use DBCA.
if you decide to goes thru manual way its better to read MOS notes since you need to apply some patches to complete the installation.
Install
sqlplus / as sysdba
SQL> @?/rdbms/admin/catols.sql
Deinstall
sqlplus / as sysdba
SQL> @?/rdbms/admin/catnools.sql
Just as note : If you install OLS while installation AUD$ table dropped from SYS schema and recreated on SYSTEM to be –> SYSTEM.AUD$
And Once you remove OLS its recreated again on SYS.AUD$
Thank you
Osama Mustafa