VSAM Data Set Considerations

With a DCB used to open a component of a VSAM data set you can perform the following tasks:

Verify that an application has master password or RACF® alter authority for the data set.
Read from or write to a data set to repair data set or catalog damage if normal VSAM processing cannot. Because of the potential for damaging a valid data set or catalog, exercise extreme caution when writing an application using this interface.

You can specify a DCB when opening a component (data or index) of a VSAM data set if the following conditions are met:

The application has master password or RACF alter authority for the data set.
The component must not reside on multiple volumes.
The component must not be a member of a concatenation.
The DCB must specify the EXCP access method.
The data set disposition must be either (OLD,KEEP,KEEP) or (SHR,KEEP,KEEP)
The DCB must specify either the INPUT or UPDAT option.
Your program must be either APF authorized or in supervisor state.

When opening a VSAM component on a volume that supports extended attribute DSCBs, the specified DCB must point to a DCBE with the EADSCB=OK keyword. When EADSCB=OK is specified, your program must support extended attribute DSCBs. These are format-8 and format-9 DSCBs, where the extent descriptors may contain 28-bit cylinder numbers.