grant codeBase "file:/install_dir/lib/51/-" {
   permission javax.security.auth.AuthPermission
      "createLoginContext.DDTEK-JDBC";
   permission javax.security.auth.AuthPermission "doAs";
   permission javax.security.auth.kerberos.ServicePermission 
      "krbtgt/your_realm@your_realm", "initiate";
   permission javax.security.auth.kerberos.ServicePermission 
      "principal_name/db_hostname@your_realm", "initiate";
};

where:

install_dir
is the product installation directory.
your_realm
is the Kerberos realm (or Windows Domain) to which the database host machine belongs.
principal_name
is the service principal name registered with the Key Distribution Center (KDC) that identifies the database service.
db_hostname
is the host name of the machine running the database.