We are using jbpm workflows for quite sometime now and we have more than 20L records in the jbpm_variableinstance table.
Planning to delete the successfully completed process_instances and corresponding references for related tables.
Can someone suggest the related tables (and order) I should be referring to for deleting the (successfully process process_instance) records.
I dont have an answer for this directly.
But as far as saving db space, you are best served cleaning out the jbpm log tables. I am not sure if you are using the log module, but it can become really large.