# Using TiCDC - Changefeed

__*changefeed*__

![left](./student-guide/diagram/TiCDCChangefeed_aa_001_20220622.png)

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The synchronization task status identifies how well the synchronization task is running. While TICDC is running, the synchronization task may run erroneously, manually pause, recover, or reach the specified targetTs, all of which can cause the synchronization task state to change. This section describes the various states of the TiCDC synchronization task and the relationships that flow between the states.
The states in the above state flow diagram are explained as follows:

Normal: The synchronization task proceeds normally, and the checkpoint-ts proceeds normally.
Stopped: The synchronization task was stopped because the user manually paused (paused) the changefeed. The changefeed in this state blocks the GC from advancing.
Error: The synchronization task reported an error. The synchronization cannot continue due to some recoverable error. Changefeed in this state will continue to try to advance until the status changes to Normal. The changefeed in this state blocks the GC from advancing.
Finished: The sync task is complete, and the progress of the sync task has reached the preset targetTs. The changefeed in this state does not block the GC from advancing.
Failed: The synchronization task failed. Synchronization cannot continue and cannot be recover due to some unrecoverable error. The changefeed in this state does not block the GC from advancing.
The numbers in the above state flow diagram are explained as follows:
① Execute the changefeed pause command.
② Execute the changefeed recover synchronization task.
③ If a recoverable error occurs during changefeed operation, it will be automatically recover.
④ Execute the changefeed recover synchronization task.
⑤ An unrecoverable error occurred while changefeed was running.
⑥ The changefeed has reached the preset targetTs, and the synchronization will stop automatically.
⑦ Changefeed is stuck for more than the time specified by gc-ttl and cannot be recover.
⑧ An unrecoverable error occurred during changefeed's automatic recover attempt.