Oracle shadow or server processes: Shadow processes work directly with the database instance to carry out the requests from the user processes. Shadow processes may be dedicated to a single user process or part of a multi-threaded server (MTS) configuration. The shadow processes are named oracleSID, where SID is the value of ORACLE_SID. For example, any shadow process connected to the database instance "DEV" would be named "oracleDEV."

See more on MetaLink Note 153655.1 (script to check memory usage included).