### DbEnv::memp_sync

`

###

    #include <db_cxx.h>

    int
    DbEnv::memp_sync(DbLsn *lsn);

### Description: DbEnv::memp_sync

The DbEnv::memp_sync method flushes modified pages in the cache to their backing files.

Pages in the pool that cannot be immediately written back to disk (for example, pages that are currently in use by another thread of control) are waited for and written to disk as soon as it is possible to do so.

To support the DbEnv::memp_sync functionality, it is necessary that the pool functions know the location of the log sequence number on the page for each file type. This location should be specified when the file is opened using the DbMpoolFile::set_lsn_offset method. It is not required that the log sequence number be aligned on the page in any way.

The DbEnv::memp_sync 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

lsn
  The purpose of the lsn parameter is to enable a transaction manager to ensure, as part of a checkpoint, that all pages modified by a certain time have been written to disk.

  All modified pages with a a log sequence number (DbLsn) less than the lsn parameter are written to disk. If lsn is NULL, all modified pages in the pool are written to disk.

### Errors

The DbEnv::memp_sync method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

EINVAL
  If the DbEnv::memp_sync function was called without logging having been initialized in the environment; or if an invalid flag value or parameter was specified.

### Class

DbEnv, DbMpoolFile

### See Also

Memory Pools and Related Methods`

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