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What are database and non-database I/Os?

Physical I/Os (synchronous and asynchronous) are also divided into database (DB) and non-database (NBD) I/Os. Database I/Os read or write IBM DB2 index and data. Transfers from or to disk of all other object types (programs, data areas, queues, job descriptions, etc.) are counted as NDB I/O – this includes I/Os to IFS.

A high non-database I/O rate could be a sign of insufficient main memory – storage management must in such cases frequently page objects out to disk. Machines with ample storage only need to load e.g. frequently used programs once.