Applying and Removing PTFs and IPLs

To progress toward 24 x 365 system availability, it is necessary to reduce or eliminate maintenance operations that cause the system to be off-line. These days, a primary cause of downtime is the application of PTFs, especially fixes that are applied to the Licensed Internal Code (LIC). More and more PTFs need to be, and are, built to apply immediately to help reduce downtime. When applying a microcode PTF on systems prior to V4R1, the system performs an IPL from the A-side to the apply PTF stage. That includes up to the C6nn nnnn set of System Reference Codes (SRCs). Microcode PTFs are applied. Before OS/400 is started, the system powers down and perform IPL again using the B-side. The IPL is selected using the control panel or the defaults of the PWRDWNSYS command. This process is fairly lengthy, and requires the LIC to be loaded for each IPL. On V4R1 and later systems, if the microcodes PTFs do not affect the MFIOP microcode, the system does not reload the MFIOP when applying the PTFs. This process avoids the need for a second IPL.

For example, a user may apply a delayed microcode PTF while on the B-side, and issue a PWRDWNSYS with a RESTART(*YES) and TYPE(*SYS). The system powers down and performs a mini-IPL without reloading the code into the MFIOP. The microcode PTF subsequently is applied during the SLIC part of the IPL. After the PTF is applied, the system IPLs again without reloading the MFIOP code. If the PTF affects the MFIOP code, the MFIOP code is reloaded during the IPL. The advantage of this approach is that the system does not have to IPL all the way up to OS/400 on the A-side, before coming down and performing IPL again on the B-side. This way, the IPL time is considerably reduced, and the PTF application is faster than it was prior to V4R1. This process is pictured below: