# txn_prepare

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    #include <db.h>

    int
    txn_prepare(DB_TXN *tid);

# 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 a parent transaction causes all unresolved children of the parent transaction to be prepared.

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

DBENV->set_tx_max, DBENV->set_tx_recover, DBENV->set_tx_timestamp, txn_abort, txn_begin, txn_checkpoint, txn_commit, txn_id, txn_prepare and txn_stat.`

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