The SP includes a plugin for storing persistent information, including user sessions, in a database using an ODBC driver. The odbc-store.so extension includes support for: MSSQL, MySQL, PostgreSQL, and Oracle.
Before trying to use this extension, strongly consider whether it's really necessary. Most applications worth clustering are not going to be able to rely on the SP's built-in session functionality. It's there primarily for simple web sites and smaller applications.
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