HP 3000 Manuals HP 3000 Manuals
Communication Line Failure If one of multiple communication lines fails, Silhouette simply distributes the transmission load over the remaining communication lines. If the last communication line becomes unavailable, the Communication Process (CP) on the primary system informs the Silhouette Operator and begins to monitor the number of records added to the primary logfile. On the secondary system, the Secondary Communication Process (SP) is usually aborted by MPE and the Recovery Process (RP) realizes there is a problem due to missed heartbeats. The RP informs the Silhouette Operator on the secondary system that the primary is no longer responding. This situation remains in force until at least one communication line returns to Silhouette service. The first two times a heartbeat is missed on either system, and thereafter periodically, the Silhouette Operators are informed. Each new record added to the logfile on the primary system is added to the CP count. To open a new data path the Operator issues the >USE command. When the first communication line is restored to Silhouette system use, the CP logs on to the secondary system and creates a new SP process as an extension of itself. This new SP determines if an RP process exists. If there is no RP, the SP creates one. If there is an RP, the SP asks for the last record number processed to the secondary logfile and applied against the secondary database. This record number is returned to the CP on the primary system and duplication begins immediately starting at that record number in the logfile. Transmission of records continues at high speed until the secondary database and logfile are back in step with the primary system. Any incomplete transactions are automatically completed.