Just got around to installing Oracle 12c on my laptop.
With a couple of hiccups I finally got it all to work.
That is: all except plsql developer.

When I start plsql developer it says:
"Initialization error
Could not initialize G:\Oracle\EvROCS\product\12.1.0]dbhome_1\bin\oci.dll
Make sure you have the 32bits Oracle Client installed
"

Although the error seems quite self-explanatory, it's weird.
1. Why do I need to install an Oracle Client at all? Up until 11.2 I didn't need to install a client on the machine the database is running on.
2. Why does it have to be 32bit? It's a 64bit windows running 64bit rdbms. Up until 11.2 that was ok for plsql developer.
3. Will I screw hings up if I install a 32bit oracle client on a 64bit windows running a 64bit rdbms?

Or am I doing something wrong?

plsql developer: 10.0.5.1710
database : 12.1.0.1.0 64bit
windows : 7 SP1 64bit

Hi there!

1. You had 32bit Oracle installation.
2. PLD, as a 32bit app, cannot call 64bit libraries.
3. No.

Oops!


You are right.
I was convinced my previous 11g installation was also 64bit.
But it turns out it wasn't.

Embarrassed!
Sorry for wasting your time!