Information Technology Reference
In-Depth Information
Fig. 13.1
A distributed transaction consisting of subtransactions T
0
(the parent) and T
1
and T
2
(the children). Server s
0
is the coordinator and servers s
1
and s
2
are participants
where S is the state of T
0
, n is the
U
NDO
-N
EXT
-LSN
,andL is a list of identifiers of
the participants (excluding the coordinator) of T
0
. The addition of server s
i
to L is
logged with the log record
h
T
0
;
add-participant
;s
i
i
:
(13.1)
The subtransaction T
i
of T
0
at remote server s
i
is represented with a transaction
record
.T
i
;s
0
;T
0
;L;S;n/
in the active-transaction table at s
i
, where the list L, initially empty, will eventually
contain the identifiers of all the participants of T
0
other than s
0
and s
i
, at the time T
0
is about to commit. The start of T
i
is logged at s
i
with
h
T
i
;s
0
;T
0
;B
i
:
(13.2)
