Huge files might start to get get generated with the name: 
/var/log/shmlog/arg/jdhcpd-interface-name.##.jdhcpd.#.arg       <--- Where # is the sequence number of the files

On EX3400 platform, the hard disk space may start to fill up quickly by these files. If left running they can become very large over 500MB~ causing a rapid storage exhaustion.
Some other large files may be seen in the same location, since this is all jdhcpd syslogging data, it can be safely removed without any traffic impact.

• As a Workaround manually delete the files with the commands:
  

  > start shell user root
  % rm -rf /var/log/shmlog

   

• This issue is tracked via the following PR, an upgrade is required for a permanent fix:
  https://prsearch.juniper.net/problemreport/PR1643824

2023/8/18 ver.1
2026/03/02 v2 - Added more information on the issue.

https://gnats.juniper.net/web/default/1684115#summary_tab