The following error message was found when examining the configtool.log located in <installation_location>/util/logs/
com.ibm.db2.jcc.am.yn: [jcc][t4][3.57.82] The application server rejected establishment of the connection.
An attempt was made to access a database, <database name>, which was either not found or does not support transactions.
When the database connection fails, be sure to look for more error messages in the configtool.log.
After reviewing the error messages in the configtool.log and researching them on the internet, the resolution was found:
Enter the DB2 location name specifying the fully qualified database server name and port. (not the database name)
The location name on z/os DB2 can be found from running this sql:
SELECT CURRENT SERVER FROM SYSIBM.SYSDUMMY1;
IBM Tech doc:
ERRORCODE=-4499, The application server rejected establishment of the connection.