When your server’s hostname exceeds 32 character, then there might have an issue of creating or Running enterprise Manager repository.
for a solution here are the steps to follow.
got to folder $ORACLE_HOME/sysman/admin/emdrep/sql/core/latest/self_monitor$ cd $ORACLE_HOME/sysman/admin/emdrep/sql/core/latest/self_monitor

backup the sqlfile self_monitor_post_creation.sql to any other name incase you need it.
$ cp self_monitor_post_creation.sql self_monitor_post_creation_bk.sql

and edit word “l_host_name  varchar2(32)” to “l_host_name  varchar2(50)” in 2 places of self_monitor_post_creation.sql file

and recreate the enterprise manager repository
 $ emca -config dbcontrol db -repos recreate