# DB_ENV->set_tx_recover

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    #include <db.h>

    int
    DB_ENV->set_tx_recover(DB_ENV *dbenv,
        int (*tx_recover)(DB_ENV *dbenv,
        DBT *log_rec, DB_LSN *lsn, db_recops op));

# Description

Set the application's function to be called during transaction abort and recovery. This function must return 0 on success and either errno or a value outside of the Berkeley DB error name space on failure. It takes four arguments:

dbenv
  A Berkeley DB environment.

log_rec
  A log record.

lsn
  A log sequence number.

op
  One of the following values:

  DB_TXN_BACKWARD_ROLL
    The log is being read backward to determine which transactions have been committed and to abort those operations that were not; undo the operation described by the log record.

  DB_TXN_FORWARD_ROLL
    The log is being played forward; redo the operation described by the log record.

  DB_TXN_ABORT
    The log is being read backward during a transaction abort; undo the operation described by the log record.

  DB_TXN_APPLY
    The log is being applied on a replica site; redo the operation described by the log record.

The DB_TXN_FORWARD_ROLL and DB_TXN_APPLY operations frequently imply the same actions, redoing changes that appear in the log record. The macro DB_REDO(op) checks that the operation is one of DB_TXN_FORWARD_ROLL or DB_TXN_APPLY, and should be used in the recovery code to refer to the conditions under which operations should be redone. Similarly, the macro DB_UNDO(op) checks if the operation is one of DB_TXN_BACKWARD_ROLL or DB_TXN_ABORT.

The DB_ENV->set_tx_recover interface may be used only to configure Berkeley DB before the DB_ENV->open interface is called.

The DB_ENV->set_tx_recover function returns a non-zero error value on failure and 0 on success.

# Errors

The DB_ENV->set_tx_recover function may fail and return a non-zero error for the following conditions:

EINVAL
  An invalid flag value or parameter was specified.

  Called after DB_ENV->open was called.

The DB_ENV->set_tx_recover 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 DB_ENV->set_tx_recover 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, DB_TXN->abort, DB_ENV->txn_begin, DB_ENV->txn_checkpoint, DB_TXN->commit, DB_TXN->discard, DB_TXN->id, DB_TXN->prepare, DB_ENV->txn_recover, DB_TXN->set_timeout and DB_ENV->txn_stat.`

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