two-phase commit

database A technique for maintaining integrity in

distributed databases. Where a system uses two or more

database, a transaction among the distibuted database should

be atomic ("all or nothing"). This is done by handling the

transaction in two phases. First the databases prepare the

transaction, confirm that it is possible to process it, and

lock the relevant record.

Once all the required databases confirm that the transaction

is viable, the system instructs them all to commit it -

i.e. to make it permanent. If it is not possible to process

it, the system will instruct the databases to rollback

(undo) the transaction.

(2000-02-28)