Opening an Object for Improved Control Interval Access

Improved control interval processing is faster because functions have been removed from the path. However, improved control interval processing causes several restrictions:

• The object must not be empty.
• The object must not be compressed.
• The object must be one of the following:
  • An entry-sequenced, fixed-length, or variable-length RRDS cluster.
  • The data component of an entry-sequenced, key-sequenced, linear, fixed-length, or variable-length RRDS cluster.
  • The index component of a key-sequenced cluster (index records must not be replicated).
• Control intervals must be the same size as physical records. When you use the access method services DEFINE command to define the object, specify control interval size equal to a physical record size used for the device on which the object is stored. VSAM uses physical record sizes of (n x 512) and (n x 2048), where n is a positive integer from 1 to 16. The physical record size is always equal to the control interval size for an index component.