Is the @CFDE Create Field Definition Entry Macro MVMAX operand an indicator of how many iterations ACF2 validation will go through for a UID string with multi-value fields?
No, the @CFDE Create Field Definition Entry Macro MVMAX specifies how many values can be defined in a multi-value field. There are other factors that determine the validation process for UIDs that contain multi-value fields.
The @CFDE Create Field Definition Entry Macro MVMAX operand specifies the maximum number of values the field can hold for a multivalue field. This value is usually the same as the value specified for MAX on the AMULTFLD macro for the field. When the UID string contains a multi-value field, validation processing detects and processes each value when necessary. The validation process determines how many values are specified in the multi-value field based on information contained in the field header information and processes the multi- value field until it hits this limit.
Details on multi-value fields can be found in the CA-ACF2 Security for z/OS Administrator Guide Chapter 2: Controlling System Entry section, "Specifying Multi-Value Logonid Fields and UID Strings".