Zend server And the Return of the Oracle Instant Client

The problem

The title being a reference to this article from 2011, a blog post from someone who encountered a similar issue once . Hopefully my blog post will prevent someone else from spending a day on this issue. We are in the middle of a migration from Oracle 11.2 to 12.1, and from PHP, Zend server more specifically, we had some connectivity problems to Oracle, the PHP function oci_connect() returned:

PHP Warning:  oci_connect(): ORA-28547: connection to server failed, probable Oracle Net admin error in /home/webro/test.php on line 2

Good luck googleing that Oracle error code, nothing hints in the right direction, only that it's an error that occurs after the connection is established. Quote from http://ora-28547.ora-code.com/:

A failure occurred during initialization of a network connection from a client process to the Oracle server: The connection was completed but a disconnect occurred while trying to perform protocol-specific initialization, usually due to use of different network protocols by opposite sides of the connection.

The problem in our case was with the characterset

The "tl;dr" is: you may be using an Oracle "Light" client instead of the "Basic" client. In Zend Server this means that in the Zend Server lib path some libraries are missing. The Light client only supports a few charactersets. If you have some other Characterset that isn't default, that may be the problem. You need to make sure the Oracle Instant client Zend Server is using is the Basic client.

Unfortunately you cannot tell this from the phpinfo() output. Both Light and Basic return exactly the same version information.

Oracle Run-time Client Library Version => 11.2.0.2.0
Oracle Instant Client Version => 11.2

How we found out..

Luckily I was able to succesfully connect from another virtual machine to the new database server. This was an older Zend server instance, where the Oracle instant client was patched from 11.1 to 11.2. The Zend server that failed had 11.2, so we assumed patching wasn't necessary. I compared the strace outputs.

The first observation was that during the communication the server--on the right in the following image--stopped and concludes there is a communication error.

Working VM on the left, failing server on the right.

The second observation in the diff was that there was also a difference between libraries loaded.

- 9166  open("/usr/local/zend/lib/libociei.so", O_RDONLY) = -1 ENOENT (No such file or directory)
- 9166  open("/usr/local/zend/lib/libociicus.so", O_RDONLY) = 4
+ 17606 open("/usr/local/zend/lib/libociei.so", O_RDONLY) = 4

More insight into the problem..

We didn't specify explicitly what characterset to use for the connection, so it will try to find out after the connection is established. We use WE8ISO8859P15 in our database, and that charset is (amongst others) provided by libociei.

$ strings /usr/lib/oracle/11.2/client64/lib/libociei.so|grep WE8ISO8859P15
WE8ISO8859P15
...

Had we specified the charset in the oci_connect parameter (fourth param) we would have seen:

PHP Warning:  oci_connect(): OCIEnvNlsCreate() failed. There is something wrong with your system - please check that LD_LIBRARY_PATH includes the directory with Oracle Instant Client libraries in /home/webro/test.php on line 4
PHP Warning:  oci_connect(): ORA-12715: invalid character set specified in /home/webro/test.php on line 4

That would have hinted us to the solution earlier. Also in strace there would have been no connection setup at all, as the client can now bail sooner with "Invalid character set specified". Apparently with the Light oracle client version 11.1 the error used to be more helpful (see beforementioned blog post here):

ORA-12737: Instant Client Light: unsupported server character set WE8ISO8859P15

The fix for Zend server

Replace the Light client with the Basic client, in our case this meant adding a library to Zend Server's libs:

# After installing the oracle instant client BASIC
ln -s /usr/lib/oracle/11.2/client64/lib/libociei.so /usr/local/zend/lib/libociei.so

Apparently the difference between Light & Basic is just this one library. The package that provides the Basic client may differ per Linux distribution, you can also download it from oracle.com.