Why does Oracle APEX Shared_Servers = 0 Break Apex 3.2
Configuring the SHARED_SERVERS Parameter


  The embedded PL/SQL gateway uses the shared server architecture of the
  Oracle Database. To achieve acceptable performance when using the
  embedded PL/SQL gateway, ensure the  SHARED_SERVERS database
  initialization parameter is set to a reasonable value (that is, not 0
  or 1). For a small group of concurrent users, Oracle recommends a
  value of 5 for SHARED_SERVERS.


It is a requirement for EPG (which is suitable only for a development environment). Better use OHS (or a J2EE web server for newer APEX versions).