Open availability means a person can be scheduled across the days and shifts specified by the employer.
A store manager may need people for opening shifts, evenings or weekends. Availability describes when someone could work. The schedule sets out the shifts they have actually been assigned. An employer can ask for a wide window of availability while offering a smaller number of paid hours within that window. Read the wording that follows the phrase. A request for open availability from Friday through Sunday has a different scope from a request covering the entire week.
In job listings
Coach separated the two ideas in an Edmonton sales associate posting. The role was full-time and specified 30 to 40 hours a week. It also required open availability. The first statement describes the volume of work. The second concerns when those hours could be scheduled.