You can define an ACS routine to determine data classes, or end users can explicitly specify a data class name on the following:

• JCL DD statements
• TSO/E ALLOCATE commands
• Access method services ALLOCATE and DEFINE commands
• Dynamic allocation requests such as through ISPF/PDF data set allocation panels

End users can explicitly specify data set attributes, and these specifications take precedence over the data set attributes assigned through the data class ACS routine.