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VMS uses the console boot device drivers (the typical VMS hardware console program is well past what BIOS offers, and closer to EFI) to write (optionally compre
by Hoff 15y ago
VMS uses the console boot device drivers (the typical VMS hardware console program is well past what BIOS offers, and closer to EFI) to write (optionally compressed, optionally pruned) system crashdump images containing the running system memory out to a pre-allocated hunk of disk storage.
Use of the console callbacks avoids issues with potential errors or corruptions within the running system device drivers, while keeping the exception handler footprint small, and also delegating device dependencies over to the console drivers.
The last barrage of hardware errors in the system error log buffer (if any) are specifically and separately captured into a file, too. This ensures that the error-logging tools can easily capture and log errors that arose in the run-up to the crash, and without having to know the details of the virtual memory structures within the crashdump.
- nonane 15y agoWindows does something similar, but it uses the swap file as temporary storage for the crash dump. On next boot, the system checks the swap file for crash dump signatures. If it finds a crash signature, it creates a minidump out of it and stores the dump in %SYSTEMROOT%\Minidumps. It also optionally prompts the user to upload the dump to it's automated analysis servers. I think it stores a bigger dump in %SYSTEMROOT%\memory.dmp too depending on how the machine is configured.
- Hoff 15y agoThat particular Windows behavior is arguably from some of NT's ancestral roots in the VMS designs. VMS can also use its pagefile as temporary storage for a system crashdump.