Historical documentation for the DB_ENV->memp_sync interface stated:
In addition, if DB_ENV->memp_sync returns success, the value of lsn will be overwritten with the largest log sequence number from any page that was written by DB_ENV->memp_sync to satisfy this request.
This functionality was never correctly implemented, and has been removed in the Berkeley DB 4.1 release. It is very unlikely application programs used this information. If your application used this information, please contact Sleepycat Software support for help in upgrading.
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