This takes you to the PROM level, but does NOT warn users about the shutdown. Once at this level you can execute one of the following PROM commands.
>c - continue after system abort.
>g0 (Sun3) - force system crash and sync the disks.
>sync (Sun4) - force system crash and sync the disks.
ok sync (Sun4c, Sun4m) - force system crash and sync the disks.
In addition to flushing the system memory buffers to disk, the PROM commands that sync the system also dump the in-core kernel and memory pages to the high end of swap on the disk. This can be useful if you want to debug the reason for a system crash. After rebooting you can use the savecore program to copy those areas of swap to the file system. Keep in mind, though, that these files can be quite large, especially if you have large amounts of physical memory. Generally, it takes a specialist in kernel architecture with access to the source code to accurately analyze these files.