The purpose of Pause and Resume is for better control of synchronization during Applying Patches & Upgrades With HA.
When a HA Pair needs to be patched or upgraded, the HA Pair can be paused by clicking on the Pause synchronization button on the Manage Pair page. This will cause synchronization to be disabled for a portion of time while the current HA Pair are still linked. This means that changes done on the Passive server will no longer be synchronized from the Active server. The HA Pair can be resumed by clicking on the Resume synchronization button. Once the HA Pair is resumed then synchronization can continue from the Active server to the Passive server. The status of this is shown in the 'Synchronization Status' column in the HA summary page.
This is necessary since the upgrade and patching process on the Passive server will likely modify it's configuration files during the upgrade.
The Pause and Resume feature can be turned on and off using the following steps:
Login to the Web Application - Administration tool and open the 'High Availability' page.
Click the Manage button associated with the pair on the HA Pair
Click the Pause synchronization button
When the HA Pair is paused, repeat the above three steps, and click the Resume synchronization button to re-enable the HA synchronization feature.