In the unusual case where the master and the auxiliary are still synchronized (perhaps  following a user stop, and no further write I/O was received), a  start  command takes the  relationship to  ConsistentSynchronized . No  -force  option is required. Also, in this case, you  can enter a  switch  command that moves the relationship or Consistency Group to  ConsistentSynchronized  and reverses the roles of the master and the auxiliary. If the relationship or Consistency Group becomes disconnected, the auxiliary changes to  ConsistentDisconnected . The master changes to  IdlingDisconnected . An informational status log is generated whenever a relationship or Consistency Group enters  the  ConsistentStopped  state with a status of  Online . You can configure this event to generate  an SNMP trap that can be used to trigger automation or manual intervention to issue a  start command after a loss of synchronization. ConsistentSynchronized  is a connected state. In this state, the master volume is accessible  for read and write I/O, and the auxiliary volume is accessible for read-only I/O. Writes that are  sent to the master volume are also sent to the auxiliary volume. Either successful completion  must be received for both writes, the write must be failed to the host, or a state must change  out of the  ConsistentSynchronized  state before a write is completed to the host. A  stop  command takes the relationship to the  ConsistentStopped  state. A  stop  command  with the  -access  parameter takes the relationship to the  Idling  state.  A  switch  command leaves the relationship in the  ConsistentSynchronized  state, but it  reverses the master and auxiliary roles (it switches the direction of replicating data). A  start command is accepted, but has no effect. If the relationship or Consistency Group becomes disconnected, the same changes are made  as for  ConsistentStopped . Idling  is a connected state. Both master and auxiliary volumes operate in the master role.  Therefore, both master and auxiliary volumes are accessible for write I/O. In this state, the relationship or Consistency Group accepts a  start  command. MM/GM  maintains a record of regions on each disk that received write I/O while they were idling. This  record is used to determine what areas must be copied following a  start  command. The  start  command must specify the new copy direction. A  start  command can cause a  loss of consistency if either Volume in any relationship received write I/O, which is indicated  by the  Synchronized  status. If the  start  command leads to loss of consistency, you must  specify the  -force  parameter. Following a  start  command, the relationship or Consistency Group changes to  ConsistentSynchronized  if there is no loss of consistency, or to  InconsistentCopying  if there  is a loss of consistency. Also, the relationship or Consistency Group accepts a  -clean  option on the  start  command  while in this state. If the relationship or Consistency Group becomes disconnected, both sides  change their state to  IdlingDisconnected . IdlingDisconnected  is a disconnected state. The target volumes in this half of the  relationship or Consistency Group are all in the master role and accept read or write I/O. IdlingDisconnected Idling Chapter 11. Advanced Copy Services  539 ConsistentSynchronized