D:\instantclient_12_2>sqlplus hr/hr@pdbtest

SQL*Plus: Release 12.2.0.1.0 Production on Fri Dec 29 15:32:34 2017

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Last Successful login time: Fri Dec 29 2017 15:16:43 +08:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> history
SP2-1650: History is off, use "SET HIST[ORY] ON" to enable History.
SQL> SET HIST ON
SQL> show hist
history is ON and set to "100"
SQL> hist
1 show hist