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m '''MySQL Archive''' is... |
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The engine is not [[ACID]] compliant. Unlike [[OLTP]] engines, it uses a "stream" format to disk with no block boundaries. The head of the Archive file generated is a byte array representing the data format and contents of that file. In MySQL 5.1, a copy of the MySQL FRM file is stored in the header of each Archive file. The FRM file, which represents the definition of a table, allows an Archive file to be restored to a MySQL server if the Archive file is copied to the server.
Despite the use of [[zlib]], Archive files are not compatible with [[gzio]], the basis of the [[gzip]] tools. It uses its own azio system that is a fork of gzio.
Archive differs from the other MySQL analytical engine, [[MyISAM]], by being a row level locking engine and by keeping a constant version snapshot throughout a single query (making it [[Multiversion concurrency control|MVCC]]). This means that Archive does not lock for concurrent bulk inserts. For bulk inserts it performs an interlaced INSERT, so unlike MyISAM, order is not guaranteed.
Users can use the archive_reader tool to take an online snapshot of a table and to change the characteristics of an archive file.
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