ECC error (actually, disk space recovery)

[STERRITT%SDEVAX.decnet@GE-CRD.ARPA]

Hello,
    	since we're discussing fatal ECC errors already, here's a one
I have been getting.  The problem comes up when I try to GC :immediately
a particular world.  When I do, it runs for a while and then crashes into
the FEP, with the message:
Fatal Disk Error at Unit 1, Cylinder 456, Head 21, Sector 17 (Fatal ECC error).
If I type Show Status, it tells me that the MC Error Status is Double Bit
Error.  The Unit, Cylinder, Head & Sector numbers are always the same.
I've been able to determine which worlds this happens in (one incremental
world and all built from it).  So, is there any way to 'lock out' that sector
from further use, so that the other good sectors in the dead file can be used?
I'd just as soon not lose the whole thing, since it's a fairly large
incremental world.  Oh yeah, it's a T306 drive, if that helps.
	thanks,
	chris sterritt
	sterritt%sdevax.decnet@ge-crd.arpa