Hi, it's an internal flag used for handling message persistence management.
One more thing, can you tell me the meaning of all states, 'C', '+' and '-'?
The values are closely related to different stages of message processing. basically:
messages of 'C' state are those not associated with any transaction.
'+' means the message is being sent within a transaction.
'-' means the message is being delivered within a transaction.
Thank you for your help.