ora-12154 issue when connecting with instant-client

Question

I am running Oracle 11g on Windows Server 2008R2. I have a client application(Zabbix) running elsewhere that is trying to connect to it.

The client machine has:

• oracle-instantclient11.2-basic-11.2.0.3.0-1.i386.rpm
• oracle-instantclient11.2-devel-11.2.0.3.0-1.i386.rpm

And as such, it does not have sqlnet.ora or tnsnames.ora files. It is attempting to establish a connection with direct addressing. With a print statement in the php, I see that it is calling

ociplogon(user,password,$connect);

with connect being set to //dbhostmachine:1521/zabbix. So everything looks good there.

C:\Users\mdobrini> lsnrctl services

LSNRCTL for 64-bit Windows: Version 11.1.0.7.0 - Production on 02-NOV-2012 13:00:55

Copyright (c) 1991, 2008, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=dbhostmachine.dddd.cccc.com)(POR
Services Summary...
Service "zabbix" has 1 instance(s).
  Instance "zabbix", status READY, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:578 refused:0 state:ready
         LOCAL SERVER
Service "zabbixXDB" has 1 instance(s).
  Instance "zabbix", status READY, has 1 handler(s) for this service...
    Handler(s):
      "D000" established:0 refused:0 current:0 max:1022 state:ready
         DISPATCHER <machine: dbhostmachine, pid: 6384>
         (ADDRESS=(PROTOCOL=tcp)(HOST=dbhostmachine.dddd.cccc.com)(PORT=61396))
Service "zabbix_XPT" has 1 instance(s).
  Instance "zabbix", status READY, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:578 refused:0 state:ready
         LOCAL SERVER
The command completed successfully

Attempting to connect locally works fine:

SQL*Plus: Release 11.1.0.7.0 - Production on Fri Nov 2 13:06:31 2012

Copyright (c) 1982, 2008, Oracle.  All rights reserved.

Enter user-name: SYSTEM
Enter password:

Connected to:
Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production

SQL> connect uuu/ppp@localhost/zabbix
Connected.
SQL>  

However, remotely I get the popular error:

ociplogon(): ORA-12154: TNS:could not resolve the connect identifier specified 

The strange thing is that it was working intermittently before. I would get an error about every 10 seconds in my application:

30923:20121101:142237.595 [Z3001] connection to database '//dbhostmachine:1521/zabbix'     failed: [-1] ORA-12516: TNS:listener could not find available handler with matching   protocol stack
30923:20121101:142237.596 watchdog: database is down

but there was definitely data being sent across the network, and persisted in the db. After restarting application and server I am no longer able to get a connection at all and am stuch on ORA-12154

Answer 1

ORA-12154 was being caused by a DNS issue. After switching to IP addressing that went away.

ORA-12516 was being caused by maximum sessions/processes being reached on the DB. After adjusting that as well as some PHP OCI8 parameter this went away as well.