# mongoc_write_concern_set_wtag()

## Synopsis

    void
    mongoc_write_concern_set_wtag (mongoc_write_concern_t *write_concern,
                                   const char *tag);

## Parameters

- `write_concern`: A mongoc_write_concern_t.

- `tag`: A string containing the write tag.

## Description

Sets the write tag that must be satisfied for the write to indicate success. Write tags are preset write concerns configured on your MongoDB server. See mongoc_write_concern_t for more information on this setting.

Beginning in version 1.9.0, this function can now alter the write concern after it has been used in an operation. Previously, using the struct with an operation would mark it as “frozen” and calling this function would log a warning instead instead of altering the write concern.