Echelon OpenLNS - Manual (Page 908)

OpenLNS Programmer's Reference 871
requests.
You only use this parameter if the
mode parameter is set to
lcaEventAutoSyncMode.
Added to API LNS Release 3.0.
StartTransaction
Summary Starts a transaction for the System object. You should call
this method in combination with CommittTransaction to
group method invocations and property modifications as part
of the same transaction.
If a transaction initiated by your client is already in progress
for the System when you call this method, an exception will
be thrown. You can complete the transaction by calling the
CommittTransaction method, or you can cancel the
transaction by calling the CancelTransaction method.
When a transaction is canceled, either explicitly or due to a
reset, all L ON W ORKS network and database changes made
since the call to StartTransaction are reversed.
If a transaction is aborted after this method is called, all
future services will return an error until the client cancels
the transaction using the CancelTransaction method.
Using transactions can increase performance dramatically in
some cases. There is a constant overhead for starting and
committing transactions, but no updates are propagated on
the network and no changes are written to disk until the
transaction is committed. This greatly increases performance
when performing multiple coordinated changes to your
database. Transactions, however, consume memory, and if an
excessive number of changes are made during a single
transaction, the resulting overhead may slow down the
overall process.
You should use transactions to synchronize changes so that
only one client can have a transaction open at a time. While
one client is making a change in a transaction, other clients
will be paused while waiting to gain the transaction lock.
Some database operations will implicitly create a
transaction, and they will therefore wait for the other client
to complete its transaction before that operation will
continue.
Transactions can also be used to perform "atomic" sets of
changes, which are changes that require a series of calls to
LNS to be made. For example, moving an application device
or router is an operation that could be performed within a
transaction. If any of the calls made during such a
transaction fails, all of the changes made up to that point can
be undone by simply cancelling the transaction.
For more detailed information on when you should use