- mdb-txn-begin env parent flagsprocedure
Create a transaction for use with the environment.
The transaction handle may be discarded using (mdb-txn-abort) or (mdb-txn-commit).
Note: A transaction and its cursors must only be used by a single thread, and a thread may only have a single transaction at a time. If MDB_NOTLS is in use, this does not apply to read-only transactions. Cursors may not span transactions.
- env
- An environment handle returned by (mdb-env-create)
- parent
- If this parameter is non-NULL, the new transaction will be a nested transaction, with the transaction indicated by parent as its parent. Transactions may be nested to any level. A parent transaction and its cursors may not issue any other operations than mdb_txn_commit and mdb_txn_abort while it has active child transactions.
- flags
- Special options for this transaction. This parameter must be set to 0 or by bitwise OR'ing together one or more of the values described here. MDB_RDONLY - This transaction will not perform any write operations.
Some possible error conditions:
- (exn lmdb MDB_PANIC)
- a fatal error occurred earlier and the environment must be shut down.
- (exn lmdb MDB_MAP_RESIZED)
- another process wrote data beyond this MDB_env's mapsize and this environment's map must be resized as well. See (mdb-env-set-mapsize).
- (exn lmdb MDB_READERS_FULL)
- a read-only transaction was requested and the reader lock table is full. See mdb_(env-set-maxreaders).
- (exn lmdb ENOMEM)
- out of memory.