ORACLE: ora-00028

This message has been added with version Oracle 11g.
This an error only informative signifying that a process has been killed by a privileged user.
The intention of the message is to ensure that the report captures information about
processes that come out unusually.
The sample sentence of this error can be divided as follows:

• “unknown” , It means that the name of the process of Oracle (Shadow, background),
  it was not possible to determine;
• “ospid (#)”, this is the pid of the operating system of the process aborted;
• “as a result of”, This precedes the error message that is why the opiodr kills the
  process.

If you see these errors a lot or all the time then this can be bug. This bug is affected
older (Oracle 11.1.0.6 and 11.1.0.7) versions. With bug error messages look like this:
“ORA-28 : opiodr aborting process unknown ospid (xxxxx_xxxxxxxxxxx) ”
The bug# is 6377339.8
Fixed in 11.2.0.1 (base release)