Oracle.exe (SHAD) process keeps increasing

oracleoracle-11g

I have an Oracle Server 11g that we use for integration tests. For some reason, the processes count [select count(*) from v$process;] keeps increasing up to the limit, causing ORA-12514: TNS:listener does not currently know of service requested in connect descriptor error when the limit is reached. I tried increasing the processes limit to 300. But after a while the database will still reach this limit and have the same error. When I tried querying 

select program, count(*) from v$process group by program order by count(*) desc;

I found that almost all of the processes are owned by Oracle.exe (SHAD)

PROGRAM                                                            COUNT(*)
---------------------------------------------------------------- ----------
ORACLE.EXE (SHAD)                                                       135
ORACLE.EXE (J001)                                                         1
ORACLE.EXE (Q001)                                                         1
ORACLE.EXE (PMON)                                                         1
ORACLE.EXE (GEN0)                                                         1
PSEUDO                                                                    1
ORACLE.EXE (LGWR)                                                         1
ORACLE.EXE (Q000)                                                         1
ORACLE.EXE (W000)                                                         1
ORACLE.EXE (DBRM)                                                         1
ORACLE.EXE (DBW0)                                                         1
ORACLE.EXE (DIAG)                                                         1
ORACLE.EXE (DIA0)                                                         1
ORACLE.EXE (MMAN)                                                         1
ORACLE.EXE (SMON)                                                         1
ORACLE.EXE (RECO)                                                         1
ORACLE.EXE (SMCO)                                                         1
ORACLE.EXE (W001)                                                         1
ORACLE.EXE (J000)                                                         1
ORACLE.EXE (PSP0)                                                         1
ORACLE.EXE (MMNL)                                                         1
ORACLE.EXE (D000)                                                         1
ORACLE.EXE (S000)                                                         1
ORACLE.EXE (CJQ0)                                                         1
ORACLE.EXE (MMON)                                                         1
ORACLE.EXE (QMNC)                                                         1
ORACLE.EXE (VKTM)                                                         1
ORACLE.EXE (CKPT)                                                         1

Any idea what's causing this process spam and how to fix it? Note, I found many users reporting the issue in the internet, see for example:

But so far I haven't found any solution or even a sensible theory

Best Answer

If you're on Windows and have DCD (dead connection detection) enabled then this could be relevant to your case. There is a note on Oracle support that talks about poor implementation of DCD on windows leaving behind a bunch of shadow processes. Without going into details as I don't think I can republish that info here, the solution was to disable DCD. So keep a monitor on the number of shad processes and disable DCD in sqlnet.ora. Fairly quick and painless to test if that is the cause..

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