On EX series switch which is working with Mist, dcd core dump was generated after rebooting this device. This is a software bug fixed through PR1799112. This KB describes the details.

EX switch observed the dcd core when it was managed by Mist. The core was generated after rebooting this device and came up.

user@switch> show system core-dumps no-forwarding

/var/crash/*core*: No such file or directory
-rw-rw---- 1 root wheel  6902810 Jul 26 10:20 /var/tmp/dcd.core-tarball.0.tgz
/var/tmp/pics/*core*: No such file or directory
/var/crash/kernel.*: No such file or directory
/var/jails/rest-api/tmp/*core*: No such file or directory
/tftpboot/corefiles/*core*: No such file or directory
total files: 1

You can find the log to indicate this core as well.

Jul  26 10:20:19  switch dumpd[14416]: Core and context for dcd saved in /var/tmp/dcd.core-tarball.0.tgz