Much of last week was taken up with a new installation of Oracle Enterprise Manager. We had been told by someone from Oracle that even if you had done it before, it would be 3-4 days work. It turns out that it actually can be done in 3-4 hours, if you get everything perfectly right. Which you can only do by process of experimentation. It turns out that this product is extremely sensitive to the exact versions of supporting products.

• JDK 1.16.0_18. If you use _20 (the current one) the helpful error message is weblogic.nodemanager.NMConnectException: Connection refused. Could not connect to NodeManager.
• Weblogic 10.3.2. If you use .3 (the current one) the helpful error message is SEVERE: Securing of OMS failed.
• Also I am using Oracle RDBMS 11.2.0.1 and Red Hat 5.3.

Those familiar with Oracle Universal Installer will note that it checks prerequisites, including versions, mysteriously these crucial dependencies aren’t checked. Whether it would be possible to upgrade these components, say if a critical security flaw was found, is apparently left as an exercise for the reader.

Another issue is that during installation, a tablespace named MGMT_TABLESPACE is created, size 10M, by the installer itself. A bit later, the install fails on:

Validating and Creating Tablespaces
RCU-6108:DB TablespaceFreeMB Prerequisite failure for: MGMT_TABLESPACE
Current space is 10MB. It should be be greater than 50MB.

If you then resize the tablespace and click Retry it will fail again – because the tablespace already exists! The workaround is to watch the installer like a hawk, and have the commands to resize the tablespace immediately ready to paste into SQL*Plus at just the right moment (!).

So now I am an expert on installing OEM 11.1.0.1. I have learnt nothing from this process, as there’s no underlying CS principle here; these bugs are essentially random, you either know them or you don’t, and as soon as Oracle release OEM 11.2 (any day now) the knowledge is obsolete… I would prefer to be investing my time, not simply using it…