Pega Platform provides features to support application server maintenance and crash recovery with minimal impact on service levels.

Application server maintenance (Quiesce)

A Pega Platform application server that requires maintenance can be "quiesced." Users on a server that has been quiesced are redirected to other servers in the Pega Platform cluster. Pega Call attempts to migrate users to other Pega Platform nodes without loss of CTI capability, by doing the following:

• Once quiesce has been initiated, Pega Call attempts to make all CSRs who are logged in Unavailable (Not-Ready) on the ACD. This minimizes the possibility of customer calls reaching a CSR who is unable to serve them.
• Pega Call stops monitoring the CSR’s extension on the server being quiesced.
• Once the user has been redirected to another node, Pega Call attempts to reconnect to the CTI environment (monitor the CSR’s extension), synchronize the user's phone state and restore his or her prior agent state (Available or Unavailable).

As these requests can fail in the ACD/CTI environment, it is possible that a CSR cannot have the correct agent state when he or she logs back into another Pega Platform server.

Crash recovery

Pega Call attempts to recover a user’s state when the user’s browser or the Pega Platform server crashes. When the user reconnects to a Pega Platform server, Pega Call will attempt to reconnect to the CTI event subscription for that user and synchronize state with the CTI server.