A Database Logon Trigger to set session values (enable PL/SQL Warnings, for eg)

ait_logon_trigger.sql

/*
 * This script needs to be run from a privileged account with the following grants (SYS will work):
 *    • GRANT CREATE TRIGGER TO {your privileged schema};
 *    • GRANT ADMINISTER DATABASE TRIGGER TO {your privileged schema};
 */

create or replace trigger ait_logon_trigger
after logon on database
when (user not in ('SYS','SYSTEM') and user not like 'APEX%')
begin
  execute immediate q'[ALTER SESSION SET PLSQL_WARNINGS = 'ENABLE:ALL']';
  execute immediate q'[ALTER SESSION SET PLSCOPE_SETTINGS='IDENTIFIERS:ALL, STATEMENTS:ALL']';
end ait_logon_trigger;