Delete Real-time Workflow encountered error logs

have noticed few real-time workflows was keeping all of the encountered errors -   we have notice CRM 2016 SP1 was running very slow and the database had grown to 56GB.  

I like to delete all of the real-time logs with status reason failed  however it taken too long from the web client.

is there an SQL script or a quicker way to delete all workflows with status reason failed from the system?

Many Thanks,

PJ