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Oracle » Monitoring » Tools »

Connection Errors


ORA-01034: ORACLE not available
TNS-12564: TNS:connection refused
TNS-12530: Unable to start a dedicated server process

Connection errors can crop up out of nowhere ; the error
message tend to be vague, and not useful at all. Here's a plan of
attack which will solve many connection issues. Try each step, and
proceed if the problem persists.

1) Check your environment ; verify the variables depicted below are set.
( NT: check the registry )
The example below details a Solaris/CSH environment.
Note the TWO_TASK setting ...

setenv ORACLE_BASE /apps/oracle
setenv ORACLE_SID db22
setenv LD_LIBRARY_PATH $ORACLE_HOME/lib:/usr/lib/X11
setenv ORACLE_PATH $ORACLE_HOME/bin:/usr/bin:/usr/local/bin
setenv ORA_CLIENT_LIB shared
set path = ($ORACLE_HOME/bin /bin /usr/bin /usr/local/bin /sbin /usr/sbin /usr/bin/X11 .)

2) Try to ping the instance:

tnsping db22

If there's an error, check $ORACLE_HOME/network/admin/tnsnames.ora

3) Restart the TNS service.

1) kill the process, running the tnslsnr binary
2) nohup $ORACLE_HOME/bin/tnslsnr start &
1) restart the service, in the control panel

4) SQL-Plus / ServerMgr

Try using this syntax: sqlplus user/password@instance

5) Solaris, shell change

Try switching the oracle user to the Bourne or Csh shell ; make a script for SQL-Plus
as follow:


setenv ORACLE_BASE /apps/oracle
setenv ORACLE_SID db22
setenv LD_LIBRARY_PATH $ORACLE_HOME/lib:/usr/lib/X11
setenv ORACLE_PATH $ORACLE_HOME/bin:/usr/bin:/usr/local/bin
setenv ORA_CLIENT_LIB shared
set path = ($ORACLE_HOME/bin /bin /usr/bin /usr/local/bin /sbin /usr/sbin /usr/bin/X11 .)

sqlplus $1 $2 $3

# OR
#sqlplus $1@$ORACLE_SID

Also verify the oracle user owns the oracle directory tree.

6) Check the pfile, verify the settings detailed below. For this example,
the machine should have at least 512mb of memory, to handle the OS and
other processes.

# 100 MB shared pool memory
shared_pool_size = 104857600

# 65 processes need 130 MB of additional memory

processes = 65
sessions = 65

Solaris: check the "shared memory" and "semaphores" settings
also, in the /etc/system file.

7) Look at sqlnet.log ; also check the alert log in

8) Verify the Oracle version, SQLNet version, and patched OS are all compatible.

9) If the problem is still a mystery, the server may need to be restarted.

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