The Alter function allows a number of different VSAM and non-VSAM data set types to be altered:
1: cluster can be shared by any number of users for read processing, or can be accessed by only one user for read and write processing.
2: cluster can be shared by any number of users for read processing, and it can also be accessed by one user for write processing.
3: cluster can be fully shared by any number of users.
4: cluster can be fully shared by any number of users and buffers used for direct processing are refreshed for each request.
3: specifies that the cluster can be fully shared.
4: specifies that the cluster can be fully shared and buffers used for direct processing are refreshed for each request.