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Berkeley DB: txn_prepare
txn_prepare
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#include <db.h>
int
txn_prepare(DB_TXN *tid, u_int8_t gid[DB_XIDDATASIZE]);
Description
The txn_prepare function 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 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.
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 txn_recover, telling the application which global
transactions must be resolved.
The txn_prepare function returns a non-zero error value on failure and 0 on success.
Errors
The txn_prepare function 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 txn_prepare function may fail and return
DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail
in the same way.
See Also
DB_ENV->set_tx_max,
DB_ENV->set_tx_recover,
DB_ENV->set_tx_timestamp,
txn_abort,
txn_begin,
txn_checkpoint,
txn_commit,
txn_discard,
txn_id,
txn_prepare,
txn_recover,
and
txn_stat.
Copyright Sleepycat Software
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