The initialization error occurs when PLSQL developer logs on to Oracle.

Let's talk about the computer system. The previous version was win2003,
PLSQL is installed on disk D, and Oracle client is installed on disk E.
After changing the win2008 system, the Oracle client deletes and reinstalls, and PLSQL is still the original D Drive file.
Oracle client configuration listenerProgramThe listener is successfully tested.
Then use PLSQL to log on. The following message is displayed:
Pl SQL initialization error
Cocould not load "D: \ app \ Administrator \ product \... \ OCI. dll" error.

Solution:
To the installation directory of plsq
D: \ Program Files \ PLSQL developer \ preferences \ Administrator
Open the default. ini file

Find the ocifile entry, which seems to be the 12th line. Modify the correct address of the OCI. dll file.
Example: e: \ app \ Administrator \ product \ 11.1.0 \ client_2 \ bin \ OCI. dll

Disable PLSQL, open it again, enter the user name and password, and log on successfully.