I can't condone manually tweaking the LiveCycle database, so I strongly encourage you to deal with Adobe Support if you ever run into a situation like this.
That being said, on a number of occasions a DSC wouldn't uninstall properly for me and thus I'm faced with the following error when trying to stop/uninstall it from Workbench or by using an Ant script:
2011-11-29 10:41:37,818 ERROR [org.jboss.ejb.plugins.LogInterceptor] RuntimeException in method: public abstract java.lang.Object com.adobe.idp.dsc.transaction.impl.ejb.adapter.EjbTransactionBMTAdapterLocal.doBMT(com.adobe.idp.dsc.transaction.TransactionCallback) throws com.adobe.idp.dsc.DSCException: java.lang.IllegalStateException: Service: YourCustomService version: 0.0 must be in a running state prior to stopping at com.adobe.idp.dsc.registry.service.impl.ServiceRegistryImpl.stop ServiceRegistryImpl.java:2003)
These are the sql scripts that will allow you to manually fix the state so that it can be uninstalled:
-- Get info about the service in question
select * from adobe.tb_sc_service where id = 'YourCustomService'
-- Chances are it's in a state of 2.
select * from adobe.tb_sc_service_configuration where service_uuid = (select uuid from adobe.tb_sc_service where id = 'YourCustomService')
-- Update the state to 0
update adobe.tb_sc_service_configuration set state = 0 where service_uuid = (select uuid from adobe.tb_sc_service where id = 'YourCustomService')
You should now be able to uninstall the dsc in Workbench.