5. OPERATION › 5.1 Operation Overview

5.1 Operation Overview

VCC schedules a user-selectable number of subtasks that are
responsible for reading VTOCs or VSAM/ICF catalogs in a way
that will minimize contention with other subtasks and to
maximize the distribution of VCC I/O across the DASD
configuration.

VCC consists of a number of load modules.  The basic
functions are the following:

    o  Initialization, subtask scheduling, and termination
       reporting
    o  Parameter parsing
    o  VTOC scan subtask
    o  VSAM/ICF and VVDS catalog scan control subtask
    o  Standard VSAM/ICF BCS and VVDS catalog scan subtask
    o  VCC interface to DFHSM ARCUTIL data collection module
    o  VCC record writer

The VCC logic flow is shown in Figure 5-1.

   +------------------------------------------------------------------------------------------------+
   |                                                                                                |
   |                                                 +---------+      (CALL)      +----------+      |
   |                                                 | VCCNTRL |------------------| VCCWRIT2 |      |
   |                                                 +---------+                  +----------+      |
   |                                                      |                                         |
   |                                                      |                                         |
   |                                                      |                                         |
   |                                                      |                                         |
   |                     (ATTACH)            (ATTACH)     |  (ATTACH)                               |
   |                 +----------------+-------------------+-------------+                           |
   |                 |                |                                 |                           |
   |            +---------+      +---------+                      +----------+                      |
   | 1 Subtask  | VCCXHSM |   +--| VCCVTOC | Variable #           | VCCVCNTL | 1 Subtask            |
   |            +---------+   |  +---------+ of Subtasks          +----------+                      |
   |                 |        |       |                                 |                           |
   |                 |        |       |-------+                (ATTACH) |                           |
   |                 |        |       |       |                         |                           |
   |            +---------+   |  +---------+  |                   +----------+ Variable #           |
   |            | ARCUTIL |   |  | VCCCVAF |  |                   | VCCVSCAN | of Subtasks          |
   |            +---------+   |  +---------+  |                   +----------+                      |
   |                          |               |                         |                           |
   |                          |             +-+    +-------------+------+-------+                   |
   |                     +---------+        |      |             |              |                   |
   |                     | VCCXSSI |        | +---------+   +---------+   +----------+              |
   |                     +---------+        | | VCCVVDS |   | VCCVBCS |   | VCCVVSAM |              |
   |                                        | +---------+   +---------+   +----------+              |
   |                                        |      |             |              |                   |
   |                                        +------+------+------+--------------+                   |
   |                                                      |                                         |
   |                                                 +----------+                                   |
   |                                                 | VCCWRITR |                                   |
   |                                                 +----------+                                   |
   |                                                                                                |
   +------------------------------------------------------------------------------------------------+

Figure 5-1.  VCC Operation Overview