Physical Unit (PU)
Although the name physical unit (PU) strongly implies a hardware component, a PU is an IBM naming convention for hardware and software combinations that perform a specific task in an SNA network. For example, PU 5 represents not only the mainframe itself, but also the mainframe software components (such as SSCP and VTAM) within the SNA network.
The following table lists the SNA defined PU types and a brief description of each.
| PU number | Description |
|---|---|
| PU 1 | Terminal Controller (IBM 6670, 3767) |
| PU 2 | Cluster controller running configuration support programs (IBM 3174, 3274, 4701, 4702) |
| PU 2.1 | Peer-to-Peer (APPN), used primarily in IBM i networks |
| PU 4 | IBM Front End Processor, usually running ACF and the Network Control Program (IBM 3754, 3725, 3720, 3745, 3746) |
| PU 5 | IBM Host (mainframe) system |