I'm running aol 4_r3, tcl 8.4.6, and nsoracle 2.7. I do know exec works before the Oracle driver is loaded, but I haven't tracked down exactly when it quits. I don't think it's on a query because if I reset the signal everything seems to work from then on.
I'm not sure the Oracle link is relevant but it's the only thing I found. I did look up the OCI connect call and it does not say anything about signals.