Symptom:
A DB timeout during the database pruning can cause HA failure resulting in both MSE to start tracking clients.

Logs before going to split brian stage

16 Jul 2014 23:30:59,687 INFO [DbMonitor-10-209-1-185] - PrimaryDbMonitor - Gap Status: null
16 Jul 2014 23:30:59,687 ERROR [DbMonitor-10-209-1-185] - PrimaryDbMonitor - monitorDbStatus: Error retrieving replication status: Reason - java.lang.NullPointerException
java.lang.NullPointerException
at com.cisco.mse.ha.db.PrimaryDbMonitor.getArchiveDestStatus(PrimaryDbMonitor.java:378)
at com.cisco.mse.ha.db.PrimaryDbMonitor.monitorDbStatus(PrimaryDbMonitor.java:276)
at com.cisco.mse.ha.db.PrimaryDbMonitor.run(PrimaryDbMonitor.java:228)
at java.lang.Thread.run(Thread.java:662)
16 Jul 2014 23:31:00,690 WARN [DbMonitor-10-209-1-185


DB timeout soon after.

16 Jul 2014 23:31:00,690 WARN [DbMonitor-10-209-1-185] - PrimaryDbMonitor - Shutting down DB monitor for peer: 10.209.1.185
16 Jul 2014 23:31:02,215 INFO [AppMonitor] - AppManagerPrimary - Checking for sub-service: Aeroscout Tag Engine
16 Jul 2014 23:31:02,616 INFO [HM:10-209-1-185] - HealthMonitorPrimaryInst - Heartbeats are up but DB monitor is down. Shutting down heartbeats also
16 Jul 2014 23:31:02,668 ERROR [HM:10-209-1-185] - HealthMonitorPrimaryInst - Failed to get status from secondary server about the database. Marking state to be primary lost secondary

Conditions:
MSE 7.4.121.0 in HA mode and database pruning task being executed.