The Director’s Chair
		Advanced Technique
		New Feature
		Special Feature
		FOCUS 101
		Customer Support
By Eric Schuler-Dalverny		OS Feature
		User Group Meeting Schedule

OS Feature: Improving VM (OS-Bridge) Performance Mainframe FOCUS sites that run VM and MVS operating systems sometimes encounter unusual problems. In this article, I describe a solution to an apparent VM performance problem that occurred when VM FOCUS was used to access data shared between a VM and an MVS system. Several customers who have the OS-Bridge product experienced delays that could also be experienced by customers who access several OS-formatted disks before their 19E (Y) disk. The Problem FOCUS customers at some VM sites experienced slowdowns in the startup of FOCUS and in the processing of requests after they upgraded to FOCUS 7.2. Initially, they attributed the degradation in performance to the new FOCUS release. Upon close review, Information Builders determined that the normal method CMS uses to search for files was the actual culprit. Before offering the solution, we should explain the environment and a nuance brought about by the new FOCUS release. In FOCUS 7.2 and higher releases, the use of the SCEERUN LOADLIB, which is part of IBM's Language Environment (LE), became the default. Typically, this LOADLIB resides on the CMS 19E (Y-disk), which is high in the CMS search order. The cause of the problem turned out to be an elongated search through all the CMS disks and MVS VTOCs on the OS-formatted disks to find the SCEERUN LOADLIB. A simple solution offered below quickly and effectively solves the apparent performance problem. Typical CMS Environment The typical scenario in a CMS environment is as follows: 1. The production FOCUS minidisk is accessed at filemode F. 2. Several OS-formatted MVS disks are accessed before the CMS 19E (Y-disk) or another disk that contains the SCEERUN LOADLIB (e.g., at filemodes J, K, L, M, N, O and P. 3. The disk containing SCEERUN LOADLIB is accessed at a filemode higher in the CMS search order than filemode P – in this scenario after the last OS disk. The Solution Use one of the following methods to update your installation procedures to force SCEERUN LOADLIB to be accessed before OS-formatted disks: 1. The recommended method is to access a subset of files from the disk containing SCEERUN LOADLIB (normally filemode Y) as an extension of filemode A. In the following example, filemode Z represents an unused filemode at your installation: ACCESS 19E z/A * LOADLIB 2. As an alternative, you can copy the SCEERUN LOADLIB from the Y disk (or whatever disk contains SCEERUN LOADLIB) to a separate minidisk accessed before the first OS-formatted disk, such as filemode B in this case. Note, however, that this approach could introduce a future maintenance concern because of the possibility of having two versions of SCEERUN LOADLIB.