The savecore command runs automatically after a system crash to retrieve the crash dump information from the dump device and writes a pair of files called unix.X and vmcore.X, where X identifies the dump sequence number. Together, these files represent the saved system crash dump information.
Crash dump files are sometimes confused with core files, which are images of user applications that are written when the application terminates abnormally.
Crash dump files are saved in a predetermined directory, which by default, is /var/crash/hostname. In previous releases, crash dump files were overwritten when a system rebooted, unless you manually enabled the system to save the images of physical memory in a crash dump file. Now, the saving of crash dump files is enabled by default.
System crash information is managed with the dumpadm command. For more information, see The dumpadm Command.