A synchronizer is disabled by default and it's usually explicitly enabled after it is installed into a structure, probably with a resync. The following list summarizes the possible states of a synchronizer:

• Disabled - the background incremental synchronization is not running. You can run resync to do a one-time full sync.
• Enabled - the background incremental synchronization is running. When a change is detected, synchronization applies the change to the other part of the synchronous link as soon as possible, typically within several seconds.
• Not Available - the synchronizer is installed but it cannot run any synchronization. The possible reasons are changes in JIRA configuration or lack of permissions from the user.

To disable an active synchronizer:

1. Open synchronization settings page for the structure.
2. Find the synchronizer and click Disable link. 

   If the synchronizer is currently running a sync, it will be allowed to finish.

To enable an inactive synchronizer:

1. Open synchronization settings page for the structure.
2. Find the synchronizer and click Enable link.
3. Alternatively, you can click Resync and Enable to resync and enable immediately after resync finishes.