Hi Cristian,
I pass through this situation many times with many processes and the finally recommendation of Sybase or SAP today its not having any object in witch both instances make dml operations because of internal sync of locks and pages. The processes sleeps in events mostly related with CLM or OCM.
SAP releases SP 130 with many changes, one its single instance database in order to config an ownership to a database on an instance. Have you taken a look at it? Perhaps it may help you.
Regards.
Javier.