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Unix Backup and Recovery by W. Curtis Preston

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Logical Backups

Informix has two logical backup commands: onunload and dbexport. onunload is much faster than dbexport, but it has many more constraints placed on it than dbexport has. There are advantages and disadvantages to each utility.

onunload exports, or unloads, a database or table into a binary output file, consisting of a logical backup of a database or table. The resulting file can be used to import data into another database using the onload utility. onunload is faster because it copies the data in page mode, instead of having to convert the data to ASCII format as dbexport does. However, since the files are binary, only the same version of onload can read an onunload backup. This utility typically is used for moving data between computers but cannot be used for moving data between databases that are not the same version. onunload locks the database in shared mode while it is running. An error is returned if it cannot obtain a shared lock.

dbexport unloads a database into text files and creates a schema file. The resulting files can be used to import data into another database using the dbimport utility. Since the files are ASCII format, they can be moved between databases running different versions of Informix. The dbexport command is not part of OnLine XPS and Informix Dynamic Server with Advanced Decision Support and Extended Parallel Options, but onunload is. It is much slower than onunload since it has to convert the data to ASCII format. It also can back ...

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