The copy pair used to start SnapOPC+ is selected based on the following logic.
When the set value for the required number of free volumes is "0", or the required number of free volumes is not set
When there is a copy pair without a SnapOPC+ session
A copy pair without a SnapOPC+ session is selected, and SnapOPC+ starts.
When all copy pairs already have a SnapOPC+ session
The copy pair with the oldest snap generation in the copy group targeted for processing is selected, and the SnapOPC+ session of that copy pair is stopped. After the SnapOPC+ session has been stopped, SnapOPC+ is started for that copy pair.
However, if the selected copy pair is not the oldest snap generation (snap generation number is other than "1") in the copy source volume, the acsnap start command terminates with an error.
When the set value for the required number of free volumes is one or more
The selected copy pair varies depending on the number of free volumes (total number of copy pairs without a SnapOPC+ session and copy pairs with a SnapOPC+ session being stopped) and the required number of free volumes. However, if the number of copy pairs without a SnapOPC+ session is zero, the acsnap start command terminates with an error.
When the number of free volumes is greater than the required number of free volumes
A copy pair without a SnapOPC+ session is selected, and SnapOPC+ starts.
When the number of free volumes and the required number of free volumes are equal
Excluding the copy pairs with a SnapOPC+ session being stopped, the oldest snap generation in the copy group is selected and the stoppage process is started for the SnapOPC+ session of that copy pair. After that the copy pair without a SnapOPC+ session is selected, and SnapOPC+ starts.
However, if a copy pair whose SnapOPC+ session can be stopped does not exist in the copy group, the command terminates with an error. Additionally, if the deletion target snap generation is not the oldest snap generation (snap generation number is other than "1") in the copy source volume, the SnapOPC+ session being stopped may remain for a while after the command is responded.
When the number of free volumes is less than the required number of free volumes
The number of free volumes is insufficient, so the acsnap start command terminates with an error.
