Host: Lost packets

 

Symptoms : Server is not responding or missing packets.

Impact : Medium

Lost packets alert indicates that communications with the SQL server either gets no response, or only gets a partial response. As well as delays experienced by users, there is possible loss of data. If the server is not responding, all traffic between the user and the server will halt. If missing packets, there will be an effect on application functionality and performance. The main effect on performance comes from packet retries which can significantly load the level of network traffic. As well, queries will have to wait for data, thus increasing possibility of blocks, deadlocks, and will elevate page file activity as buffer pool space is locked.

Expected behavior :

Server should respond to every ping. AimBetter will raise an alert if 12 pings in sequence fail.

Possible causes

Network load  Priority : Medium

Recommended action :
Check network traffic loads with network analyzer. If possible, move high-volume traffic (e.g remote storage, backups) onto a secondary network.

Incorrect network settings  Priority : Medium

Recommended action :
Optimize the settings (DNS, IP change or card bandwidth) to improve network capacity. If necessary, upgrade to faster components wherever bottlenecks are occurring.

Large data transfer load in the network.  Priority : Medium

Recommended action :
If possible, move high-volume traffic (e.g remote storage, backups) onto a secondary network, or reschedule to periods of low SQL demand.
Connection is lost  Priority : Medium
In cases of complete disconnection, when 12 packets have been lost in succession.
Recommended action :
Possible causes are:
– network failure (router, bridge, other hardware)
– server crash/power off
Check the physical environment. In case of server crash, restart and investigate cause of the crash. In case of network failure, replace faulty components and restore network functionality.

Background

AimBetter communicates every 5 seconds with the server via a ping command. Success of the ping, and the time taken (latency) are monitored to assess the health of network connections to the server. Note that this metric deals only with communications between the server and AimBetter, not between server and users.