Quite frequently, if you are running enabling debugging on something, it is going to be a little too verbose. Then you want to turn it off, or change something, but you cant see what you are typing. The solution to this would be Synchronous logging. It essentially just carries over what you typed to the next line after it is done flooding your terminal(or vty) buffer.
Agg1(config)#line vty 0 4
Agg1(config-line)#logging synchronous
Agg1(config-line)#exit
Agg1#debug ethernet-interface
Ethernet network interface debugging is on
Agg1#terminal monitor
Agg1#show
(didnt hit enter after typing show)
I then logged in a second time and shut/un-shut one of my port channel interfaces to cause some chatter.
Agg1(config)#int FastEthernet 0/16
Agg1(config-if)#shut
Agg1(config-if)#no shut
Looking back at my original terminal:
Agg1#show
23:15:14: %LINK-5-CHANGED: Interface FastEthernet0/16, changed state to administratively down
3:15:14: %LINK-5-CHANGED: Interface FastEthernet0/23, changed state to administratively down
23:15:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/16, changed state to down
Agg1#show
23:15:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to down
Agg1#show
23:15:26: %LINK-3-UPDOWN: Interface FastEthernet0/16, changed state to down
23:15:26: %LINK-3-UPDOWN: Interface FastEthernet0/23, changed state to down
23:15:26: %LINK-3-UPDOWN: Interface FastEthernet0/16, changed state to up
23:15:26: %LINK-3-UPDOWN: Interface FastEthernet0/23, changed state to up
23:15:27: %SYS-3-MSGLOST: 1 messages lost because of queue overflow
Agg1#show
23:15:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to up
Agg1#show
Notice how it re-showed my prompt, as well as what I had previously typed. It may seem stupid, but work on these switches long enough, and you will understand why this was a notable feature.