Technical data

Shelf Management Alarm Module
AXP 1410 Installation and Use (6806800H70D)
186
8.5.3 Switchover Signals
A switchover takes place when the Standby SAM determines that the Active SAM is no longer
operational. The signs of this are:
z The REMOTE_HEALTHY or REMOTE_PRESENT changes to FALSE. This indicates that the
peer SAM is no longer healthy or present
z The TCP connection between the Active and the Standby SAMS closes. The keep alive
time-out parameter for this connection is set to 1 second to recognize a malfunction of the
Active SAM as quickly as possible. In this case the Standby SAM waits for 3 seconds and
then checks the state of the REMOTE_HEALTHY to make sure the connection is broken due
to a failure of the Active SAM and not due to a communication failure.
If the Standby SAM detects that the Active SAM is still healthy it doesn’t perform the
switchover but instead reboots itself. After the reboot it makes a second attempt to
initialize as a backup and will continue until either it succeeds in establishing the
connection with the Active SAM or it detects that the Active SAM is no longer healthy. If it
detects that it isn’t healthy it will initialize as the Active SAM.
z When the Active SAM receives a switchover command from the Standby SAM and agrees
to switchover, it closes the TCP connection, clears the LOCAL_HEALTHY bit and exits the
program which indicates the switchover to the Standby SAM.
If the Standby SAM decides that a switchover should take place it closes the TCP
connection and exits this function. Activate callbacks are called for all facilities and the
SAM starts to work in active mode, with no backup. At this moment the SAM sets the
LOCAL_SWITCHOVER bit, requesting the hardware to recognize it as the Active SAM. In
response, the hardware must set the ACTIVE bit. When the formerly active SAM restarts it
successfully establishes the connection with the current SAM and starts to operate in the
backup mode.
8.6 Telco Alarm Functionality
The SAM provides Telco alarm functionality with the following components:
z Telco alarm cutoff push button
z DB15 Telco alarm contacts
z Telco alarm LEDs