The option --validateatmostonceperiod=interval is missing from the Synopsis section and the Options section of the help information for the create jbdc-connection-pool command.
The description of this option is as follows:
Specifies the time interval in seconds between successive request to validate a connection at most once. Setting this attribute to an appropriate value minimizes the number of validation requests by a connection.
The default value is 0, which specifies that the connection is never validated.
For more information, see Issue report.
For complete information about the create jbdc-connection-pool, see the create-jdbc-connection-pool(1) man page.