#include <db.h> int DB_TXN->prepare(DB_TXN *tid, u_int8_t gid[DB_GID_SIZE]);
The DB_TXN->prepare() method initiates the beginning of a two-phase
commit.
In a distributed transaction environment, Berkeley DB can be used as a
local transaction manager. In this case, the distributed transaction
manager must send prepare messages to each local
manager. The local manager must then issue a DB_TXN->prepare() and
await its successful return before responding to the distributed
transaction manager. Only after the distributed transaction manager
receives successful responses from all of its
prepare messages should it issue any
commit messages.
In the case of nested transactions, preparing the parent causes all unresolved children of the parent transaction to be committed. Child transactions should never be explicitly prepared. Their fate will be resolved along with their parent's during global recovery.
All open cursors in the transaction are closed and the first cursor close error will be returned.
The DB_TXN->prepare()
method returns a non-zero error value on failure and 0 on success.
The errors that this method returns include the error values of DBcursor->close() and the following:
A Berkeley DB Concurrent Data Store database environment configured for lock timeouts was unable to grant a lock in the allowed time.
You attempted to open a database handle that is configured for no waiting exclusive locking, but the exclusive lock could not be immediately obtained. See DB->set_lk_exclusive() for more information.
The gid parameter specifies the global transaction ID by which this transaction will be known. This global transaction ID will be returned in calls to DB_ENV->txn_recover() telling the application which global transactions must be resolved.