Total Disk Queue Usage Example Calculation

Provides an example for calculating the total disk queue.

To calculate the total disk space necessary to handle all queues during a worst-case failure (4 hours), using:

Sum(InboundQueueSizes) + Sum(OutboundQueueSizes)

where:

InboundQueueSizes are the two queues calculated in “Inbound queue size example calculation.”
OutboundQueueSizes are the three queues calculated above.

The total disk space needed in the worst case, including 2MB for the RSSD inbound queue, is:

2MB + 28MB + 8MB + 151MB + 324MB + 194MB = 707MB

Sybase recommends that you allocate enough space for your worst case scenario. If you use the save interval feature (outbound queues are not truncated even after messages are delivered to the next site), be sure to allocate enough queue space to sustain your peak transaction activity. If you do not use the save interval, then under normal circumstances, your queue utilization is very small, perhaps 1MB or 2MB per queue.

The example calculation assumes that all outbound queues must tolerate the same duration of failure. This assumption may not be true in your environment. Typically, connections across a WAN must tolerate longer duration failures than local connections.