ora-12560 and ora-12500

subject:- ORA-12500:TNS listener failed to start a dedicated server process. AND ORA-12560:TNS Protocol adapter error.

1) We installed Ora9i on Win2000. After installing I created a service  name in Ora8i client to connect to Orac9i server.

2) Ping and TNSping has worked fine at client side.

3) But in client's sqlplus  when connected using servicename it says ORA-12500.

4) I also tried to create another service name at server side that connects to its own database  and tested it.It says ORA-12560.

5) I tried to connect through DBAStudio at server side I got same ORA-12560 error.

6) I checked (Client's)tnsnames.ora,(server's) sqlnet.ora,(server's)listener.ora. Their setting are fine.

7) We reinstalled Oracle9i but the problem persists.


1)when installing win2000 we got DNS lookup error but somehow we solved it. Does this error anyway related to ORA-12560.
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Unable to connect to Oracle: Ora-12500 Ora-12547
1. With TCP/IP connection:
  Getting :
   ORA-12500: TNS:listener failed to start a dedicated server process
      sqlnet.log shows:
        Fatal NI connect error 12500, connecting to:
        Tns error struct:
          nr err code: 0
          ns main err code: 12564
          TNS-12564: TNS:connection refused
          ns secondary err code: 0
          nt main err code: 0
          nt secondary err code: 0
          nt OS err code: 0
      Listener.log shows:
      TNS-12500: TNS:listener failed to start a dedicated server process
       TNS-12547: TNS:lost contact
        TNS-12560: TNS:protocol adapter error
         TNS-00517: Lost contact
          HPUX Error: 32: Broken pipe
2. With BEQ connection:
      sqlnet.log shows:
       Fatal NI connect error 12547, connecting to:
       Tns error struct:
          nr err code: 0
          ns main err code: 12547
          TNS-12547: TNS:lost contact
          ns secondary err code: 12560
          nt main err code: 517
          TNS-00517: Lost contact
          nt secondary err code: 32
          nt OS err code: 0
The PROCESSES parameter in init.ora is set to a sufficient value. (say 200)
and the select count(*) from v$process shows that total number of processes has
not reached the limit of 200.
Select count(*) from v$process = 72  
But still further connections to Oracle fail with the above errors.
Upgraded to
This is issue is identified as a Bug:2654576 (unpublished)
This is fixed in patchset V9.2.0.3 and Oracle 10i.
Apply the patchset V9.2.0.3 wherein this is fixed.
As a workaround :
  1. Increase the init.ora PROCESSES parameter.
  2. If after increasing the PROCESSES parameter does not help, can set the following  
     parameter in init.ora in addition to point 1.
       _attach_count_slack = 2000

For 8i:

Problem Description
You get the following error while trying to connect to the database using
SQL*Plus SQLPLUS or Server Manager SVRMGRL.  
  ORA-12500 TNS:listener failed to start a dedicated server process.
The listener is running fine and tnsping tests are also successful.
There appears to be resource-related issues on the server e.g. memory, paging,
The Oracle database service, as seen through Windows NT Control Panel, shows
as Started.
Solution Description
You may need to recreate the database service.
One of the ways to do so is to use the ORADIM utility:
 ORADIM -NEW -SID <sid_name> -INTPWD <internal_password> -STARTMODE
 For other options, run 'ORADIM --HELP' command from the command prompt.
The Oracle Service may be corrupt. This could have happened for a variety of
reasons, including:
1. The registry being corrupt.
2. Installation of other Oracle Products in different oracle homes.
3. Installation/de-installation of some oracle products from the home where the
   Oracle database resides.
ORA-12500 can occur while a connection is being made to the database.
Recreating the service helps to resolve the issue.

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I have this issue,

 TNS:listener failed to start a dedicated server process

I'm running 9i on my laptop, and the solutions I'm finding don't seem to be helping.  I need a step by step on this.

I have a strange issue. I am running Oracle on my Laptop(XP Pro). Whenever I startup the Listener, I can tnsping my database successfully. The next time I try to do a tnsping, the listener hangs. I have to then go to the NT services from the control panel > admin tools and restart the listener. Again it will only tnsping the first time and so the loop goes...

Similarly, when I start up the listener the first time, I can log on to the database via TOAD the first time. Any subsequent attempt to load TOAD just hangs...

It is painstaking to keep stopping and starting the listener each time. Please HELP!!!
Try to recreate the listener using NET Configuration Assistant. Drop the existing and create a new one.
See in the logs of the {ORACLE_HOME}\network\logs and in alert.log for clue what happened.
Lack of RAM, oo much processes, running antivirus (not only stop, but also delete it), firewall and other software can be the cause for this.
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