DB_TXN->prepare(DB_TXN *tid, u_int8_t gid[DB_XIDDATASIZE]);
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
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
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.
The DB_TXN->prepare method returns a non-zero error value on failure and 0 on success.
The DB_TXN->prepare method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
If a catastrophic error has occurred, the DB_TXN->prepare method may fail and
in which case all subsequent Berkeley DB calls will fail in the same way.
Transaction Subsystem and Related Methods
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