# Example Using Subdiagram Phase Blocks

This example also appears in the System Analysis Reference book.

Consider a server that has two shifts each day, a day shift lasting 8 hours and a night shift lasting 16 hours. Within each shift, it has a peak period and an off-peak period with different durations.

The RBDs for the Peak phase and the Off-Peak phase are:

The phase diagrams for the Night Shift and Day Shift are:

The main phase diagram with phase subdiagram blocks is:

During the Peak phase, the reliability of Block A follows W(1.5,30) and the reliability of Block B follows W(1.5,40). During the Off-Peak phase, the reliability of Block A follows W(1.5,15) and the reliability of Block B follows W(1.5,20). In the Day Shift diagram, both blocks have CM and PM with duration = 1 hour; in the Night Shift diagram, both blocks have CM and PM with duration = 2 hours. In the Day Shift diagram, the duration of the Off-Peak phase is 4 hours and the duration of the Peak phase is 3 hours. In the Night Shift diagram, the duration of the Off-Peak phase is 8 hours and the duration of the Peak phase is 6 hours.

The system log for 2 days (48 hours) is shown in the figure below.

1. At 5.4 hours, in the Peak phase of the Day Shift diagram, Block A fails. After this Peak phase, Block A gets CM and Block B gets PM in the maintenance phase.
2. At 19.9 hours, in the Peak phase of the Night Shift diagram, Block A fails again. After this Peak phase, Block A gets CM and Block B gets PM in the maintenance phase.
3. At 40.6 hours, in the Peak phase of the Night Shift diagram, Block A fails again. After this Peak phase, Block A gets CM and Block B gets PM in the maintenance phase.