A Study on the Reliability of the Circuit Maintenance System-1B

The Circuit Maintenance System ( C M S ) - I B has a multiple office feature and can support up to six No. 4 ESSS* (for a description of No. 4 ESS and CMS, see Refs. 1 and 2). For a high degree of reliability, the C M S - I B employs a duplex computer system with an operating system designed to have fast reboot time and backup recovery capabilities. In addition to its hardware and software structures, the reliability of the CMS-IB depends on the proficiency of the on-site corrective maintenance activities. Switching over from a faulty to a standby system, rebooting the system in the event of a software error, and repairing * Since the total number of No. 4 E S S trunk terminations supported by a cannot exceed 160K, not more than one of these No. 4 E S S S is full-sized. 1317 CMS-IB the faulty system are some maintenance activities required to bring the CMS-IB back to normal operation. In this paper, we quantify some of the significant factors governing the CMS-IB reliability. More importantly, we evaluate whether the level of reliability attained by the CMS-IB would have any adverse impact on the No. 4 ESS served by it. We determine whether the current hardware arrangement, software structure, or administrative procedures are adequate from the No. 4 ESS'S point of view. Should they be inadequate, we recommend some feasible means of upgrading the reliability of the CMS-IB. The remaining portions of this paper are organized as follows. Section II provides a simplified description of the hardware arrangement of the CMS-IB.