# DbEnv::txn_recover

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    #include <db_cxx.h>

    int
    DbEnv::txn_recover(DB_PREPLIST preplist[],
        long count, long *retp, u_int32_t flags);

# Description

The DbEnv::txn_recover interface returns a list of prepared but not yet resolved transactions. The DbEnv::txn_recover method should only be called after the environment has been recovered. Because database environment state must be preserved between recovery and the application calling DbEnv::txn_recover, applications must either call DbEnv::txn_recover using the same environment handle used when recovery is done, or the database environment must not be configured using the DB_PRIVATE flag.

On return from DbEnv::txn_recover, the preplist argument will be filled in with a list of transactions that must be resolved by the application (committed, aborted or discarded). The preplist argument is a structure of type DB_PREPLIST; the following DB_PREPLIST fields will be filled in:

DB_TXN *txn;
  The transaction handle for the transaction.

u_int8_t gid[DB_XIDDATASIZE];
  The global transaction ID for the transaction. The global transaction ID is the one specified when the transaction was prepared. The application is responsible for ensuring uniqueness among global transaction IDs.

The application must call DbTxn::abort, DbTxn::commit or DbTxn::discard on each returned DbTxn handle before starting any new operations.

The count parameter specifies the number of available entries in the passed-in preplist array. The retp parameter returns the number of entries DbEnv::txn_recover has filled in, in the array.

The flags value must be set to one of the following values:

DB_FIRST
  Begin returning a list of prepared, but not yet resolved transactions.

DB_NEXT
  Continue returning a list of prepared, but not yet resolved transactions, starting where the last call to DbEnv::txn_recover left off.

The DbEnv::txn_recover method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.

# Errors

The DbEnv::txn_recover method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the DbEnv::txn_recover method may fail and either return DB_RUNRECOVERY or throw a DbRunRecoveryException, in which case all subsequent Berkeley DB calls will fail in the same way.

# Class

DbEnv, DbTxn

# See Also

Transaction Subsystem and Related Methods`

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