Hi
The 12.2 (and 12.1) documentation do not mention any limit on the size of
the banner. But the 11.2 states it must be no larger than 512 bytes.
https://docs.oracle.com/cd/E11882_01/network.112/e10835/sqlnet.htm#BIIICDCD
"The text file has a maximum limit of 512 bytes."
Cheers
Patrick