I might be wrong, but I don't think it will be possible to specify ssl attributes in an ODBC connection.
You can download a PB 12.5 dbparm connection guide here: http://infocenter.sybase.com/help/topic/com.sybase.infocenter.dc33820.1250/pdf/dbparm.pdf It's old, but might help you on the right path. If anyone knows of a more recent version that info would be welcome.
Take a look at connecting to DB2 using JDBC or "native driver" (if powerbulder supports that one, the native driver would be best).
(we use a Tibero database, which is not supported by Appeon and cannot use SSL in an ODBC connection. We have to use JDBC in which we specify protocol=TCPS instead of the default protocol=TCP. It works great (once you've figured out the connection string).
An example of our Tibero dbparm connection string:
PBCatalogOwner='CREDIT',Driver='com.tmax.tibero.jdbc.TbDriver',URL='jdbc:tibero:thin:@(description=(protocol=tcps)(address=(host=RX-DEV-0X)(port=1234))(DATABASE_NAME=my_database))',PBNewSPInvocation='Yes',DisableBind=1,DelimitIdentifier='No',TrimSpaces='No'
NOTE:
the "(address= .... " is normally only necessary for specifying a list of clustered hosts. We don't have a clustered database, but we still had to use it to be able to specify the "protocol" parameter.
HIH
MiguelL