IBM System z9 is a line of IBM mainframe computers. The first models were available on September 16, 2005. The System z9 also marks the end of the previously used eServer zSeries naming convention. It was also the last mainframe computer that NASA ever used. Background System z9 is a mainframe using the z/Architecture, previously known as ESAME. z/Architecture is a 64-bit architecture which replaces the previous 31-bit-addressing/32-bit-data ESA/390 architecture while remaining completely compatible with it as well as the older 24-bit-addressing/32-bit-data System/360 architecture. The primary advantage of this arrangement is that memory intensive applications like DB2 are no longer bounded by 31-bit memory restrictions while older applications can run without modifications. Name change With the announcement of the System z9 Business Class server, IBM has renamed the System z9 109 as the System z9 Enterprise Class server. IBM documentation abbreviates them as the z9 BC and z9 EC, respectively. Notable differences There are several functional enhancements in the System z9 compared to its zSeries predecessors. Some of the differences include: Support Element & HMC The Support Element is the most direct and lowest level way to access a mainframe. It circumvents even the Hardware Management Console and the operating system running on the mainframe. The HMC is a PC connected to the mainframe and emulates the Support Element. All preceding zSeries mainframes used a modified version of OS/2 with custom software to provide the interface. System z9's HMC no longer uses OS/2, but instead uses a modified version of Linux with an OS/2 lookalike interface to ease transition as well as a new interface. Unlike the previous HMC application on OS/2, the new HMC is web-based which means that even local access is done via a web browser. Remote HMC access is available, although only over an SSL encrypted HTTP connection. The web-based nature means that there is no longer a difference between local console access and remote access, which means a remote user potentially has full control if authorized, allowing more flexibility for locating systems within data centers. IBM refers to the new HMC as a "closed platform" which does not allow the user to install software or access the command line interface to increase security and stability. The HMC is also firewalled by default with a minimal number of open ports for remote access. Program Directed Re-IPL Program Directed Re-IPL is a new feature for Linux on