CMUG00028E The ratio of alias volumes to base volumes must be expressible in whole numbers. Fractional ratios are not permitted.

Explanation

You can specify more aliases than base volumes, or you can specify more base volumes than aliases. In either case, the larger number must be evenly divisible by the smaller number, with no remainder.

You can assign 4 aliases to 1 base volume. The ratio is 4:1. You can assign 1 alias to 3 base volumes. The ratio is 1:3. You cannot assign 2 aliases to 5 base volumes. The ratio is 1:2.5.