The Alter function allows you to alter a number of different VSAM and non-VSAM data set types:
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.