Network Latency

Referring back to our typical Dekho deployment (see figure 1), the database is located on a separate tier.  If there is a significant latency delay between the database and application tiers, this delay will impact the performance of Dekho.

Latency is easy to measure, using a simple Windows command prompt:

tracert "server host name with database on"

Results provide the number of network hops and the associated network latency time for a single trip.  High performance LAN should have minimal amounts of latency (~5ms), but if latency times over 1.5 seconds are experienced, then significant delay times for the Dekho Map Client will result.

Unless network latency can be minimised by upgrading the network link between the two tiers, a workaround can be implemented by placing a database instance local to the Dekho Application server (e.g. Oracle or SQL Server Express).  This configuration eliminates any latency and network bandwidth issues, but will consume some of the local machine resources. Consequently, the database should be tuned to not consume all of the available CPU/memory from the Dekho/ArcGIS Server application.

System Resource Contention