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SakaiAdminX uses an embedded Derby database to store some configuration information, as well as acting as a cache for heaviest queries. It runs in embedded mode which is very lightweight.
You could, however, use MySQL or Oracle if you prefer and you will just ened need to adjust your settings and use the appropriate drivers in place of the Derby ones. SakaiAdminX ships with DB scripts for both Derby and MySQL. If you want to run SakaiAdminX on Oracle, you might need to tweak the scripts - if you do, send them to me for inclusion in the release. All SAL in SakaiAdminX should be database independant.
Download, install and configure Apache Derby
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