This is a text description of sbr81013.gif.
This figure shows two multiplexed online redo log configurations, one of which is labeled LEGAL, the other is labeled ILLEGAL. The LEGAL configuration shows DISK A and DISK B, containing three online redo log groups, each with 2 members. The ILLEGAL configuration shows DISK A and DISK B, but containing only one online redo log group with 2 members. This is illegal because there must be at least 2 online redo log groups.