Management Information › System Overview Display › Tuning Specifications

Tuning Specifications

Not only does an IPL present an opportunity to change the system parameters, it can also provide an opportunity to alter z/OS tuning specifications. For example, the virtual memory that each job or TSO user uses is called an address space. z/OS shares an area of virtual storage across all address spaces called common service area or common system area (CSA). When we speak of CSA, we actually are referring to the below-the-16MB line common system area (CSA) as well as the above-the-16 MB line extended common system area (ECSA). CA Auditor reports on the use of CSA and ECSA on the System Overview Display. Although CSA permits sharing information between address spaces, it reduces the size of what is called the private area, a major component of each individual address space.

The System Overview Display also reports on the size of the private area, both in terms of below-the-16MB line private area storage and above-the-16MB line private area storage. If CSA size is too large, there is less space for the individual address spaces. Inadequate space for address spaces can cause increased paging and poor response time. Therefore, the technical support staff must choose an optimum CSA size. All z/OS systems require at least some performance tuning. This requires the use of performance and tuning software tools such as the IBM resource management facility (RMF).