CLM 4.0.6

I'm running some ClearCase imports in a "sandbox" RTC server (Tomcat / Derby) before doing the real thing. I've been getting this, a lot:

D:\sandbox\IBM\ClearCaseSynchronizer\ccctools\eclipse>ccc import ccase -d D:\migr\data -r  https://sandbox:10443/ccm -u jadmin -P secret -s Int_Stream -c SCMWeb -N proto_integration
2014-06-16 08:42:38,489  INFO Starting to import data to Rational Team Concert.
 The details are logged in "D:\migr\data\logs\importCCase.2014-06-16T08.42.37.log".
2014-06-16 08:43:14,993  INFO Imported 100 directories.
2014-06-16 08:44:45,972  INFO Starting to import versions.
2014-06-16 08:45:53,722  INFO Imported 1000 versions.
[...]
2014-06-16 12:45:31,462  INFO Imported 12000 versions.
2014-06-16 12:57:24,858  INFO Creating configuration for baseline: proto_integration.
Problem running 'import ccase':
Could not import data to Jazz SCM because of the following error:
CRJAZ0099E An HTTP error occurred when this URL was being accessed: https://sandbox:10443/ccm/service/com.ibm.team.scm.common.IScmService. Error details: java.net.SocketTimeoutException.

The log file says:
[...]
SQL Exception #1
SQL Message: A lock could not be obtained within the time requested
SQL State: 40XL1
Error Code: 30000
[...]

Is this because I'm using Derby, or will this also happen on the "real" import (SQL Server)?

Is there some Advanced Setting in the CCM server that would help prevent this?

Am I doomed to have to carve the export and import down to folders?

Thanks,
Larry.