Chapter 11. Advanced Copy Services 539
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
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
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
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.