The EMCA command parameters have changed from Ora10gR1 to Ora10gR2; if you still have Release 1 installed you must be aware that the EMCA parameters used in that release were completely different to the parameters in 10gR2. I would go so far as to say that one of the very few things these releases have in common is the tool name.
emca [options] [list of parameters][options] = -[a|b|c|e <node>| f <node>|h|m|n <ndoe>|r|s|x <db>|RMI_PORT <port>|JMS_PORT <port>| AGENT_PORT <port>|DBCONSOLE_HTTP <port>] EMCA 10 g Release 1syntax[list of parameters] = [HOST | SID | PORT | ORALCE_HOME | LISTENER | HOST_USER | HOST_USER_PWD | BACKUP_HOUR | BACKUP_MINUTE | ARCHIVE_LOG | EMAIL_ADDRESS | MAIL_SERVER | MAIL_SERVER_NAME | ASM_OH | ASM_SID | ASM_PORT | ASM_USER_ROLE | AMS_USER_NAME | ASM_USER_PWD | EM_HOME | DBSNMP_PWD | SYSMAN_PWD | SYS_PWD | CLUSTER_NAME | DB_NAME | SERVICE_NAME | ]