- MongoDB C Driver 1.13.1 »
- API Reference

# mongoc_write_concern_t

Write Concern abstraction

## Synopsis

`mongoc_write_concern_t` tells the driver what level of acknowledgement to await from the server. The default, MONGOC_WRITE_CONCERN_W_DEFAULT, is right for the great majority of applications.

You can specify a write concern on connection objects, database objects, collection objects, or per-operation. Data-modifying operations typically use the write concern of the object they operate on, and check the server response for a write concern error or write concern timeout. For example, mongoc_collection_drop_index() uses the collection’s write concern, and a write concern error or timeout in the response is considered a failure.

Exceptions to this principle are the generic command functions:

- mongoc_client_command()
- mongoc_client_command_simple()
- mongoc_database_command()
- mongoc_database_command_simple()
- mongoc_collection_command()
- mongoc_collection_command_simple()

These generic command functions do not automatically apply a write concern, and they do not check the server response for a write concern error or write concern timeout.

See Write Concern on the MongoDB website for more information.

## Write Concern Levels

Set the write concern level with mongoc_write_concern_set_w().

MONGOC_WRITE_CONCERN_W_DEFAULT (1) | By default, writes block awaiting acknowledgement from MongoDB. Acknowledged write concern allows clients to catch network, duplicate key, and other errors.
MONGOC_WRITE_CONCERN_W_UNACKNOWLEDGED (0) | With this write concern, MongoDB does not acknowledge the receipt of write operation. Unacknowledged is similar to errors ignored; however, mongoc attempts to receive and handle network errors when possible.
MONGOC_WRITE_CONCERN_W_MAJORITY (majority) | Block until a write has been propagated to a majority of the nodes in the replica set.
n | Block until a write has been propagated to at least `n` nodes in the replica set.

## Deprecations

The write concern `MONGOC_WRITE_CONCERN_W_ERRORS_IGNORED` (value -1) is a deprecated synonym for `MONGOC_WRITE_CONCERN_W_UNACKNOWLEDGED` (value 0), and will be removed in the next major release.

mongoc_write_concern_set_fsync() is deprecated.

## Functions

- mongoc_write_concern_append()
- mongoc_write_concern_copy()
- mongoc_write_concern_destroy()
- mongoc_write_concern_get_fsync()
- mongoc_write_concern_get_journal()
- mongoc_write_concern_get_w()
- mongoc_write_concern_get_wmajority()
- mongoc_write_concern_get_wtag()
- mongoc_write_concern_get_wtimeout()
- mongoc_write_concern_is_acknowledged()
- mongoc_write_concern_is_default()
- mongoc_write_concern_is_valid()
- mongoc_write_concern_journal_is_set()
- mongoc_write_concern_new()
- mongoc_write_concern_set_fsync()
- mongoc_write_concern_set_journal()
- mongoc_write_concern_set_w()
- mongoc_write_concern_set_wmajority()
- mongoc_write_concern_set_wtag()
- mongoc_write_concern_set_wtimeout()

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