typedef struct __db DB;
The DB handle is the handle for a Berkeley DB database, which may or may not be part of a database environment. DB handles are free-threaded if the DB_THREAD flag is specified to the DB->open method when the database is opened or if the database environment in which the database is opened is free-threaded. The handle should not be closed while any other handle that refers to the database is in use; for example, database handles must not be closed while cursor handles into the database remain open, or transactions that include operations on the database have not yet been committed or aborted. Once the DB->close, DB->remove, or DB->rename methods are called, the handle may not be accessed again, regardless of the function's return.
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