--- wikisrc/tutorials/how_to_enable_and_run_dtrace.mdwn	2019/07/21 12:28:26	1.27
+++ wikisrc/tutorials/how_to_enable_and_run_dtrace.mdwn	2020/03/30 15:40:27	1.28
@@ -151,3 +151,19 @@ made by a process
 - `execsnoop` - snoop on execution of processes as they occur
 - `opensnoop` - snoop on openning of files as they occur
 - `procsystime` -  print process system call time details.
+
+## Troubleshooting
+
+The Compact C Type Format (CTF) has a 2^15 limit on types which can overflow, this prevents DTrace from
+working correctly.
+
+Check the number of types using `ctfdump` e.g
+    ctfdump -S /netbsd
+
+Note the line which states `total number of types`, the value should by less than 32768.
+
+If overflow is not an issue, `libdtrace(3)` can provide some insight into what is going on via an
+environment variable. Define `DTRACE_DEBUG` before tracing.
+
+     env DTRACE_DEBUG= execsnoop
+