Specifying multi  means that Global Mirror starts cycling based on the cycle period, which defaults to 300 seconds. The valid range is from 60 seconds to 24*60*60 seconds (86,400 seconds = one day). 

If all of the changed grains cannot be copied to the secondary site within the specified time, then the replication is designed to take as long as it needs and to start the next replication as soon as the earlier one completes. You can choose to implement this approach by deliberately setting the cycle period to a short amount of time, which is a perfectly valid approach. However, remember that the shorter the cycle period, the less opportunity there is for peak write I/O smoothing, and the more bandwidth you need. 

The -cyclingmode  setting can only be changed when the Global Mirror relationship is in a stopped state. 

## Recovery point objective using Change Volumes 

RPO is the maximum tolerable period in which data might be lost if you switch over to your secondary volume. 

If a cycle completes within the specified cycle period, then the RPO is not more than 2x cycle long. However, if it does not complete within the cycle period, then the RPO is not more than the sum of the last two cycle times. 

The current RPO can be determined by looking at the lsrcrelationship  freeze time attribute. The freeze time is the time stamp of the last primary Change Volume that has completed copying to the secondary site. Note the following example: 

1. The cycle period is the default of 5 minutes and a cycle is triggered at 6:00 AM. At 6:03 AM, the cycle completes. The freeze time would be 6:00 AM, and the RPO is 3 minutes. 

2. The cycle starts again at 6:05 AM. The RPO now is 5 minutes. The cycle is still running at 6:12 AM, and the RPO is now up to 12 minutes because 6:00 AM is still the freeze time of the last complete cycle. 

3. At 6:13 AM, the cycle completes and the RPO now is 8 minutes because 6:05 AM is the freeze time of the last complete cycle. 

4. Because the cycle period has been exceeded, the cycle immediately starts again. 

## 6.3.2 Remote Copy network planning 

Remote copy partnerships and relationships do not work reliably if the connectivity on which they are running is configured incorrectly. This section focuses on the intersystem network, giving an overview of the remote system connectivity options. 

## Terminology 

The intersystem network is specified in terms of latency  and bandwidth . These parameters define the capabilities of the link regarding the traffic that is on it. They be must be chosen so that they support all forms of traffic, including mirrored foreground writes, background copy writes, and intersystem heartbeat messaging (node-to-node communication). 

Link latency is the time that is taken by data to move across a network from one location to another and is measured in milliseconds. The longer the time, the greater the performance impact. 

