DbMpoolFile::set_clear_len()
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## DbMpoolFile::set_clear_len()

    #include <db_cxx.h>

    int DbMpoolFile::set_clear_len(u_int32_t len);

The `DbMpoolFile::set_clear_len()` method sets the number of initial bytes in a page that should be set to nul when the page is created as a result of the DB_MPOOL_CREATE or DB_MPOOL_NEW flags specified to DbMpoolFile::get(). If no clear length is specified, the entire page is cleared when it is created.

The `DbMpoolFile::set_clear_len()` method configures a file in the cache, not only operations performed using the specified DbMpoolFile handle.

The `DbMpoolFile::set_clear_len()` method may not be called after the DbMpoolFile::open() method is called. If the file is already open in the cache when DbMpoolFile::open() is called, the information specified to `DbMpoolFile::set_clear_len()` must be consistent with the existing file or an error will be returned.

The `DbMpoolFile::set_clear_len()` 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.

### Parameters

#### len

The len parameter is the number of initial bytes in a page that should be set to nul when the page is created. A value of 0 results in the entire page being set to nul bytes.

### Class

DbEnv, DbMpoolFile

### See Also

Memory Pools and Related Methods

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