Format of an ECB

• Fixed application work areas, which are used by the application program

  This is work space for use by application programs in any way it is required. The work areas are unformatted and of fixed sizes. However, if an application requires additional work area beyond what is provided by the ECB, it can be requested from the z/TPF system.

• Fixed system work areas
  • Resource interface area, which is used by both the application program and the control program

    This area contains the addresses of file records and working storage blocks that the application program has requested from the z/TPF system.

  • Entry management area, which is used by the control program

    This area contains status information and other data required for managing an entry.

• User-definable area, which can be used by the application program

  The space is for use by application programs in any way it is required.

It is used to hold data related to the Entry that might impact system availability if damaged by the application program, such as control information that is used to manage the ECB and working storage blocks. ECB page 2 also contains a field that points to the resource limit table (RLT), which contains the two levels of limits for each resource that is monitored (see ECB resource monitor for more information).

There is also a user-definable area in ECB page 2. The difference between this user-definable area and the one in ECB page 1 is that this one offers an additional level of protection because its storage key is not the same as the storage key for the entry. Protection is achieved because the storage protection key must be explicitly changed in order to update this area.

There also is a field in ECB page 3 that points to the resource counter table (RCT), which contains the counter for each monitored resource (see ECB resource monitor for more information).