what is the target type as database system in OEM tool?
A target type is commonly be specified when using the emctl. This frequently occurs when a command impacts a specific target (for example emctl reload agent dynamicproperties).
The most frequent used target types are the following:
oracle_database (Oracle Instance)
host (Host Machine)
To get complete list of target type, you may query SYSMAN.EM_TARGET_TYPES table in the Enterprise manager repository.