Automatic OpenVMS Tuning and I/O Analysis Tool
tm DLB Plus is a trademark of Touch Technologies, Inc. |
Touch Technologies, Inc. (TTI) has prepared this publication for use by TTI personnel, licensees, and customers. This information is protected by copyright. No part of this document may be photocopied, reproduced or translated to another language without prior written consent of Touch Technologies, Incorporated.
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The following are trademarks of Touch Technologies, Inc., and may be used only to describe products of Touch Technologies, Inc.:
DYNAMIC TAPE ACCELERATOR INTOUCH 4GL DYNAMIC LOAD BALANCER PLUS REMOTE DEVICE FACILITY |
The following are trademarks of Digital Equipment Corporation, and may be used only to describe products of Digital Equipment Corporation:
DBMS DCL DECNET VMS/OpenVMS RDB RMS VAX |
Revised January 1997
| Contents | Index |
Dynamic Load Balancer Plus (DLB Plus) is a sophisticated OpenVMS software based system that dynamically tunes your system for peak performance. DLB Plus tunes systems by using an intelligent feedback system to constantly monitor and change SYSGEN and process specific parameters. By keeping a history of performance metrics, DLB Plus is able to accurately and quickly respond to changing workloads. The result is improved response times and better overall system performance.
In addition, DLB Plus includes I/O analysis tools to aid in pinpointing and providing solutions to I/O bottlenecks.
By analyzing file I/O operations, "hot" files (those with high I/O counts) are identified. Hot files consume valuable I/O resources. Once identified, hot files can be moved to your fastest disk devices. Files with high read/write ratios are also located by DLB Plus. These files are excellent candidates for local and global data buffering, or can be moved to a RAM disk.
DLB Plus also includes a fragmentation prevention feature that prevents disk and file fragmentation on OpenVMS systems by intercepting file creation and file extension requests. The intercepted requests are modified to reduce fragmentation. This feature is normally enabled system-wide, but can be disabled (and later re-enabled) for individual processes via DCL commands.
DLB Plus is written in a combination of BLISS, the same language in which the OpenVMS operating system is written, and INTOUCH, a high-performance 4GL designed to handle complex data analysis. INTOUCH is written in BLISS.
The purpose of this manual is to provide:
This manual is intended for use by the system manager or other technical personnel.
IF YOU HAVE NO SYSTEM MANAGER OR YOU HAVE QUESTIONS ABOUT INSTALLING DLB PLUS, PLEASE CALL US AT:
1-800-525-2527 toll free within the U.S. and Canada
1-619-566-3603 elsewhere
Dynamic Load Balancer Plus (DLB Plus) is the original OpenVMS on-line dynamic tuning product. DLB Plus monitors the system load and makes adjustments to process memory usage and CPU scheduling parameters. These adjustments enhance system performance.
DLB Plus makes adjustments dynamically, continuously as system loads change. Dynamic tuning results in a balanced and well-tuned OpenVMS system. Benefits include:
DLB Plus also has facilities for setting process biases (see Chapter 15, DLB Plus Performance Options). Bias settings cause DLB Plus to favor one type of process over another (e.g. interactive over CPU bound processes).
1.1 Components
DLB Plus consists of three major components:
1.2 DLB Plus Operations
DLB Plus encourages efficient management of system CPU and physical
memory resources. It does this by periodically sampling system load
information as well as process memory management information.
1.2.1 Process and System Adjustments
Using an intelligent feedback system, DLB Plus adjusts the following:
To determine which adjustments to make, DLB Plus scans the system at frequently scheduled intervals to collect evaluation statistics. DLB Plus checks the following statistics:
The sampling interval frequency is determined dynamically by DLB Plus based on its current mode of operation and memory adjustment statistics. Scheduling statistics are collected every few seconds.
1.2.2 Modes of Operation
DLB Plus has three modes of operation, determined automatically, based
on the amount of system activity. The operation modes are described in
the following table.
| Ample | Free list size greater than 50% of the total physical memory. In Ample mode, DLB Plus samples and adjusts process memory usage every 90 seconds. |
| Low | Free list size is less than 50% but greater than 10% of the total memory. In Low mode, DLB Plus samples and adjusts process memory usage every 30 seconds. |
| Insufficient | Free list size is less than 10% of total physical memory. In Insufficient mode, DLB Plus samples and adjusts process memory usage every 6 seconds. |
Regardless of the current mode of operation, DLB Plus performs a check of free list size every few seconds. If the free list size is reduced, and fits the criteria for a new mode of operation, DLB Plus immediately goes into a memory adjustment cycle.
1.2.3 Memory Adjustments
To determine which memory adjustments to make, DLB Plus checks the page
fault rates, working set list size, working set size, and physical
memory in use for each process. Then, DLB Plus makes adjustments to the
working set list size of each process as needed.
1.2.4 Scheduling Adjustments
By making adjustments to scheduling parameters, DLB Plus evens out
access to CPU resources. To determine which scheduling adjustments to
make, DLB Plus checks the number of processes waiting for CPU resources
(in a COM state) and other scheduling statistics. Based on the
statistics, and DLB Plus's internal history of previous scheduling
changes, appropriate parameters are changed.
1.3 DLB Plus I/O Analysis
DLB Plus includes comprehensive I/O analysis tools for pinpointing I/O
bottlenecks. When DLB Plus samples your system, a "snapshot" is taken
of the processes running on the current node (the node on which DLB
Plus is executing). For each process, I/O read/write information is
collected and stored into DLB Plus data file records. These data file
records are used to create reports and graphs.
DLB Plus I/O analysis tools are the foremost file I/O and lock diagnostic tools available for OpenVMS systems. In order to effectively manage an OpenVMS system, the system manager needs to know as much about the system as is possible. DLB Plus performs analysis that helps system managers do their work by providing this much needed information.
The following are examples of situations where DLB Plus' diagnostic capabilities are absolutely invaluable:
You get a call from a user. The user complains that "the terminal is stuck" and has been for the last ten minutes. This has happened many times before. You know the cause - ANOTHER USER IS HOLDING A LOCKED RECORD and won't give it up!
How do you find the user with the locked record? Without the use of DLB Plus, it is a time consuming task...trying to figure out which user is holding the locked record (the blocker). The more users you have, the tougher the task is of finding the blocker. And, if you have a VAX cluster, the task is almost impossible!
1.3.1.1 DLB Plus finds locked record holders - Instantly
With DLB Plus, finding out who is holding the locked record (the
blocker) is quick and easy:
Over the last few days you have noticed that one of your disk drives is overworked...too many I/Os. By using the Digital provided DCL command:
$ MONITOR DISK/ITEM=QUEUE
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you see queue depths in excess of one (anything over 0.5 means that users are waiting for disk I/O to complete). Therefore, you know that you need to move some files off of the busy disk and on to a less busy one. But, how do you know which files to move? And how do you know where to move the files once you find them?
1.3.2.1 No more guessing - DLB Plus finds your HOT files
DLB Plus will do the leg work for you and find those files with high
I/O rates (hot files). To generate your list of HOT files and to reduce
the I/O bottleneck on the overworked disk:
You have been told that there will be expanded use of one of the major applications on the system. Management needs from you the estimated system impact that the expanded use will cause. They also need to know what additional hardware (money) will be necessary to support the expansion.
1.3.3.1 DLB Plus provides application I/O capacity planning
DLB Plus performs OpenVMS image (application) level I/O rate analysis.
The combined I/O rates for all files associated with a given
application are summarized and displayed. The aggregate I/O rate is
then multiplied by the expansion factor...giving the estimated I/O
system impact caused by the expanded application.
To perform I/O capacity analysis with DLB Plus, you do the following:
As memory prices dropped, you purchased extra memory for your system. Now, you find that you have surplus memory capacity. However, at the same time, you are still I/O bound! You need to know which files are the best candidates for memory data caching. And, after data caching the files, you need to know if the data caching was effective or not.
1.3.4.1 DLB Plus locates candidate files for data caching
DLB Plus locates files with high I/O rates and high read percentages.
Mostly-read files with high I/O rates are the best candidates for data
caching (RMS global buffering).
In order to locate candidate files, set RMS buffering, and monitor the effectiveness of the data caching, the following steps should be taken:
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