DbEnv::txn_begin |
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#include <db_cxx.h>int DbEnv::txn_begin(DbTxn *parent, DbTxn **tid, u_int32_t flags);
The DbEnv::txn_begin method creates a new transaction in the environment and copies a pointer to a DbTxn that uniquely identifies it into the memory referenced by tid.
If the parent argument is non-NULL, the new transaction will be a nested transaction, with the transaction indicated by parent as its parent. Transactions may be initiated in threads of control other than the parent's and may be nested to any level.
The flags parameter must be set to 0 or one of the following values:
This behavior may be set for an entire Berkeley DB environment as part of the DbEnv::set_flags interface.
This behavior is the default for Berkeley DB environments unless the DB_TXN_NOSYNC flag was specified to the DbEnv::set_flags interface.
Note: While child transactions may be initiated in threads of control other than the parent's, an individual transaction may not span threads, i.e., each transaction must begin and end in the same thread, and each transaction may only be used by a single thread.
Note: cursors may not span transactions, i.e., each cursor must be opened and closed within a single transaction.
Note: a parent transaction may not issue any Berkeley DB operations, except for DbEnv::txn_begin, DbTxn::abort and DbTxn::commit, while it has active child transactions (child transactions that have not yet been committed or aborted).
The DbEnv::txn_begin 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.
The DbEnv::txn_begin method may fail and throw an exception or return a non-zero error for the following conditions:
The DbEnv::txn_begin 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_begin method may fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.
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