text: Consider the following points: 
  
  (cid:2) MM/GM relationships can be part of a consistency group, or they can be stand-alone and, 
  therefore, are handled as single instances. 
  
  (cid:2) A consistency group can contain zero or more relationships. An empty consistency group 
  with zero relationships in it has little purpose until it is assigned its first relationship, except 
  that it has a name. 
  
  (cid:2) All relationships in a consistency group must have corresponding master and auxiliary 
  volumes. 
  
  (cid:2) All relationships in one consistency group must be the same type, for example only Metro 
  Mirror or only Global Mirror. 
  
  Although consistency groups can be used to manipulate sets of relationships that do not need 
  to satisfy these strict rules, this manipulation can lead to undesired side effects. The rules 
  behind a consistency group mean that certain configuration commands are prohibited. These 
  configuration commands are not prohibited if the relationship is not part of a consistency 
  group. 
  
  For example, consider the case of two applications that are independent, yet they are placed 
  into a single consistency group. If an error occurs, synchronization is lost and a background 
  copy process is required to recover synchronization. While this process is progressing, 
  MM/GM rejects attempts to enable access to the auxiliary volumes of either application. 