(computer, IBM) (Enterprise System Architecture) An IBM mainframe computer introduced in 1988. Successor to the IBM 370XA had enhanced access registers that allowed access to other forms of virtual memory. This enhancement allowed more data storage in main and virtual memory, reducing I/O operating and improving speed and efficiency. The IBM 370ESA was rebranded as the IBM390, and later as the zSeries.
Last updated: 2004-06-06