This does NOT just flush the DNS cache; it flushes the whole Directory Service cache. The man page for dscacheutil says:
-flushcache
Flushes the entire cache. This should only be used in extreme
cases. Validation information is used within the cache along
with other techniques to ensure the OS has valid information
available to it.
[Version 1.1]
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DNS Flusher
-flushcache
Flushes the entire cache. This should only be used in extreme
cases. Validation information is used within the cache along
with other techniques to ensure the OS has valid information
available to it.