Asterisk just started:
webdevel*CLI> dialplan show parkedcalls
[ Context 'parkedcalls' created by 'res_features' ]
  '700' =>          1. Park()                                     [res_features]

-= 1 extension (1 priority) in 1 context. =-

Parking 1 call.

webdevel*CLI>
    -- Executing [1100@xyz:1] Set("SIP/xyz011101-081e9268", "TIMEOUT(absolute)=10800") in new stack
    -- Channel will hangup at 2008-09-16 00:25:14 UTC.
    -- Executing [1100@xyz:2] AGI("SIP/xyz011101-081e9268", "agi://devel.acecape.com") in new stack
    -- AGI Script Executing Application: (SetCallerPres) Options: (allowed_passed_screen)
    -- AGI Script Executing Application: (Set) Options: (CALLERID(name)=Unknown)
    -- AGI Script Executing Application: (Set) Options: (CALLERID(num)=Unknown)
    -- AGI Script Executing Application: (Dial) Options: (SIP/xyz110001|180|kK)
    -- Called xyz110001
    -- SIP/xyz110001-081ee528 is ringing
    -- SIP/xyz110001-081ee528 answered SIP/xyz011101-081e9268
    -- Started music on hold, class 'default', on channel 'SIP/xyz011101-081e9268'
  == Parked SIP/xyz011101-081e9268 on 701@parkedcalls. Will timeout back to extension [xyz] s, 1 in 600 seconds
    -- <SIP/xyz110001-081ee528> Playing 'digits/7' (language 'en')
    -- <SIP/xyz110001-081ee528> Playing 'digits/0' (language 'en')
    -- <SIP/xyz110001-081ee528> Playing 'digits/1' (language 'en')
    -- Added extension '701' priority 1 to parkedcalls
  == Spawn extension (xyz, s, 1) exited non-zero on 'Parked/SIP/xyz011101-081e9268<ZOMBIE>'
    -- Executing [h@xyz:1] NoOp("Parked/SIP/xyz011101-081e9268<ZOMBIE>", "v2 hangup extension. channel type=NULL") in new stack
    -- Executing [h@xyz:2] GotoIf("Parked/SIP/xyz011101-081e9268<ZOMBIE>", "1?lines_out:+1") in new stack
    -- Goto (xyz,h,5)
    -- Executing [h@xyz:5] GotoIf("Parked/SIP/xyz011101-081e9268<ZOMBIE>", "1?lines_done:+1") in new stack
    -- Goto (xyz,h,8)
    -- Executing [h@xyz:8] NoOp("Parked/SIP/xyz011101-081e9268<ZOMBIE>", "") in new stack
webdevel*CLI>
webdevel*CLI> dialplan show parkedcalls
[ Context 'parkedcalls' created by 'res_features' ]
  '700' =>          1. Park()                                     [res_features]
  '701' =>          1. ParkedCall(701)                            [res_features]

-= 2 extensions (2 priorities) in 1 context. =-

Hanging up parked call.

webdevel*CLI>
    -- Stopped music on hold on SIP/xyz011101-081e9268
  == SIP/xyz011101-081e9268 got tired of being parked
webdevel*CLI>

Extension 701 is still there.

webdevel*CLI> dialplan show parkedcalls
[ Context 'parkedcalls' created by 'res_features' ]
  '700' =>          1. Park()                                     [res_features]
  '701' =>          1. ParkedCall(701)                            [res_features]

-= 2 extensions (2 priorities) in 1 context. =-

Attempting to park another call:

webdevel*CLI>
    -- Executing [1100@xyz:1] Set("SIP/xyz011101-081fb0f0", "TIMEOUT(absolute)=10800") in new stack
    -- Channel will hangup at 2008-09-16 00:25:49 UTC.
    -- Executing [1100@xyz:2] AGI("SIP/xyz011101-081fb0f0", "agi://devel.acecape.com") in new stack
    -- AGI Script Executing Application: (SetCallerPres) Options: (allowed_passed_screen)
    -- AGI Script Executing Application: (Set) Options: (CALLERID(name)=Unknown)
    -- AGI Script Executing Application: (Set) Options: (CALLERID(num)=Unknown)
    -- AGI Script Executing Application: (Dial) Options: (SIP/xyz110001|180|kK)
    -- Called xyz110001
    -- SIP/xyz110001-081fca90 is ringing
    -- SIP/xyz110001-081fca90 answered SIP/xyz011101-081fb0f0
[Sep 15 17:25:54] WARNING[12940]: res_features.c:338 park_call_full: Requested parking extension already exists: 701@parkedcalls
  == Spawn extension (xyz, s, 1) exited non-zero on 'Parked/SIP/xyz011101-081fb0f0<ZOMBIE>'
    -- Executing [h@xyz:1] NoOp("Parked/SIP/xyz011101-081fb0f0<ZOMBIE>", "v2 hangup extension. channel type=NULL") in new stack
    -- Executing [h@xyz:2] GotoIf("Parked/SIP/xyz011101-081fb0f0<ZOMBIE>", "1?lines_out:+1") in new stack
    -- Goto (xyz,h,5)
    -- Executing [h@xyz:5] GotoIf("Parked/SIP/xyz011101-081fb0f0<ZOMBIE>", "1?lines_done:+1") in new stack
    -- Goto (xyz,h,8)
    -- Executing [h@xyz:8] NoOp("Parked/SIP/xyz011101-081fb0f0<ZOMBIE>", "") in new stack