Example

The following is an example of a DASD channel program that will not always execute correctly. Using this channel program is inadvisable.

         CCW   X'47',LRArea,X'60',L'LRArea   Locate Record
         CCW   X'86',Data,X'60',L'Data       Read Data
         CCW   X'92',Search,X'60',L'Search   Read Count
         CCW   X'22',Sector,X'20',1          Read Sector for this count
LRArea   DC    0XL16             Area for Locate Record command
         DC    X'06010002'       Operation, auxiliary, block count (2)
Seek     DC    X'xxxxxxxx'       CCHH for seek
Search   DC    X'xxxxxxxxxx'     Search argument
Sector   DC    X'FF0000'         Sector and transfer length factor
Data     DC    ----

The application program would have to store appropriate values at labels "Seek" and "Search" before issuing EXCP. (On an IBM® 3990 storage subsystem, it will execute more efficiently if an appropriate value is stored at "Sector" also. On newer storage subsystems, such as the IBM 2107, the sector value has no effect.)

If all or part of the third CCW executes (Read Count), then reexecution of the channel program by the ERP will give different results.