Dynamic Tape Acceleratortm

Dynamic Tape Acceleratortm

for VAX and Alpha OpenVMS® Systems

Dynamic Tape Accelerator was developed and is supported
by Touch Technologies, Inc. Dynamic Tape Accelerator is
distributed by Touch Technologies, Inc.

Touch Technologies, Inc.
9988 Hibert Street, Suite 310
San Diego, California 92131
Sales, Support (800) 525-2527

Note

tm Dynamic Tape Accelerator is a trademark of Touch Technologies, Inc.

® VAX, OpenVMS are a registered trademarks of Digital Equipment Corporation.

NOTICE

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.

TTI believes the information described in this publication is accurate and reliable; much care has been taken in its preparation. However, no responsibility, financial or otherwise, is accepted for any consequences arising out of the use of this material.

The information contained herein is subject to change without notice and should not be construed as a commitment by Touch Technologies, Inc.

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     INTOUCH INSA 
 
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      OpenVMS      RDB      RMS      VAX

Revised April 1997 for V4.0

Copyright ©1992, 1997 Touch Technologies, Inc.

Contents Index

Preface

Dynamic Tape Accelerator (DTA) is a software tape monitor and acceleration tool that eliminates costly tape I/O bottlenecks for all VAX and Alpha OpenVMS based systems --- transparently and efficiently. All applications, any OpenVMS utilities, and yes... even OpenVMS BACKUP... will finish faster. DTA runs on:

Dynamic Tape Accelerator uses a TTI proprietary I/O intercept routine to monitor, cache, and then quickly deliver data to your tape drive. Data flow to the tape drive is greatly accelerated, speeding up all tape operations.

DTA is written in a combination of MACRO-32 and BLISS-32, the same languages that the OpenVMS operating system is written in. This makes DTA fast and efficient, and able to accelerate your tape drives without a lot of system overhead. On most systems, DTA's impact on your application will be less than a 10% CPU time increase. This is a small price to pay for the phenomenal elapsed time savings that DTA provides.

Purpose

The purpose of this manual is to provide:

Audience

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 DTA, PLEASE CALL TOUCH TECHNOLOGIES, INC. AT:



(800) 525-2527 toll free within the U.S. and Canada.

(619) 566-3603 elsewhere.

Chapter 1
Method of Operation

1.1 Components

Dynamic Tape Accelerator increases performance of I/O write operations to tape devices. This includes both magtape and cartridge tape devices. The tape drives can be either streaming or start/stop. Even optical disks configured as tape devices and helical scan 8mm drives are sped up by DTA.

DTA consists of two components:

Table 1-1 DTA Components
<> DTA command files monitor operations and process commands
<> the DTA device driver intercepts I/O operations

The DTA command files are used by the system manager to monitor tape operations and to communicate with the DTA device driver. The system manager is prompted for commands. By entering appropriate commands, the system manager can monitor, accelerate, and deaccelerate tape devices.

The DTA monitor displays tape performance characteristics. In addition, the monitor tracks:

When a tape device is accelerated, the DTA device driver intercepts all I/O operations to the device. I/O operations are monitored and then considered for caching or are sent directly to the accelerated device.

1.2 Theory of Operation

In order to work at their peak throughput capacity, tape devices need a steady flow of data to the tape sub-system. Dynamic Tape Accelerator provides this steady flow of data by intercepting tape I/O requests, caching them, and then releasing them at a constant rate of speed to the tape sub-system. The result is faster overall tape operations.

Each I/O request from the application goes to the DTA device driver. The DTA device driver gives the I/O request to the DTA caching system. The DTA caching system decides if the I/O request needs to be cached or sent directly to the tape device. At the appropriate time, the DTA caching system releases cached requests to the accelerated tape device. This controlled release of data causes accelerated I/O operations to occur.

1.2.1 A Simple Example

Take the example of farm crops irrigated by a nearby river. The crops need a constant flow of water in order to grow to maximum size.

1.2.1.1 Uncontrolled Flow

During heavy rains the crops are flooded. They are getting more water than they can handle at once. During drought conditions there is little or no water in the river, and the crops suffer from lack of water.

1.2.1.2 Controlled Flow

The farmer builds a dam. The dam creates a reservoir of water during heavy rains. Sluice gates are partially opened to allow the proper amount of water to flow to the crops. During drought conditions the gates are opened wider, augmenting the water from the river with the water held in the reservoir. The result is a constant and consistent flow of water to the crops.

1.2.2 DTA Controls the Flow of Data

Dynamic Tape Accelerator acts like an integrated dam and sluice gate facility. When OpenVMS passes large amounts of data to the tape device driver, DTA intercepts the I/O requests and creates a data reservoir (data cache). When very little data is passed to the tape device driver, that data is augmented with data from the cache. The result is a constant flow of data to the tape device.

In order to control the flow of data to the tape device, DTA maintains a dynamic data cache. The cached memory is taken from the free page list. The number of memory pages taken from the free page list is dynamically controlled. If the system is short on memory, pages are given back to the free list. While the system is long on memory, pages are taken from the free list as needed...and given back as necessary.

?32pc

Example 1-1 Dynamic Tape Accelerator Flow Diagram 

+-----------------+ 
| OpenVMS BACKUP  | 
|  or other       | 
| application     |                    +------------------------+ 
+-----------------+                    | OpenVMS free page list | 
               \                       +------------------------+ 
                \                                 | 
              +--------------------------+        | 
              | Dynamic Tape Accelerator |        | 
              |--------------------------|        | 
              |   (dynamic data cache)   |--------+ 
              +--------------------------+ 
            /                              \
           /                                \
+-------------+                        +---------------+ 
| DTA MONITOR |                        | Device driver | 
+-------------+                        +---------------+ 
                                      / 
                                     / 
                              +-------------+ 
                              | Tape device | 
                              +-------------+

Chapter 2
Getting Started

Note
In order to install Dynamic Tape Accelerator, it is ESSENTIAL to make the system parameter changes described in this chapter. FAILURE TO MAKE THE REQUIRED CHANGES WILL CAUSE THE DYNAMIC TAPE ACCELERATOR TO ABORT OR OTHERWISE FAIL.

Before installing DTA, it is necessary to change the following OpenVMS NON-DYNAMIC SYSGEN parameters. These changes are required for the successful operation of DTA.

2.1 Required SYSGEN Parameter Changes

The following NON-DYNAMIC SYSGEN parameter settings are required. These settings allow DTA to efficiently cache I/O requests to tape devices. Use the OpenVMS SYSGEN facility to make these changes.

2.1.1 SYSGEN Parameter Values

Dynamic Tape Accelerator requires that you change two SYSGEN parameters. They are: NPAGEDYN and SPTREQ.

Note
The NPAGEDYN parameter is changed on both the VAX and the Alpha. The SPTREQ parameter only exists and is changed on the VAX.

DTA allocates space out of NPAGEDYN for various tables that it needs in order to monitor and control the DTA caching system. No more than 204,800 bytes (400 pages) of NPAGEDYN are needed for this task.

Dynamic Tape Accelerator needs to allocate and deallocate pages of memory for its data cache. Because DTA is implemented as a pseudo device driver, it must allocate free memory using system page table entries. The SYSGEN parameter SPTREQ controls the number of system page table entries on your system. Dynamic Tape Accelerator can use up to 38000 system page table entries at a time.

The SPTREQ and NPAGEDYN increases required for DTA consume about 1000 pages of permanently allocated OpenVMS memory. When caching data, DTA allocates and deallocates pages from the existing free list. If the free list gets low, pages are deallocated from the DTA cache and given back to the free list.

2.2 Changing SYSGEN Parameter Values

Note
For simplicity, the examples in this manual show using SYSGEN directly.

In order to set the new values for each parameter, you must first run SYSGEN and look up the old values. (See Appendix B, An Example of Changing SYSGEN Parameters, for instructions on using SYSGEN.)

Table 2-1 SYSGEN Parameter Changes
Parameter New Value
NPAGEDYN old value + 204800
SPTREQ old value + 38000

For example, if your NPAGEDYN is 450000 and SPTREQ is 4000, your new values would be:

Table 2-2 SYSGEN Parameter Changes
Parameter Old Value Add New Value
NPAGEDYN 450000 204800 654800
SPTREQ 4000 38000 42000

The SYSGEN parameter changes can be made either directly through the OpenVMS SYSGEN utility, or by adding the following lines to your SYS$SYSTEM:MODPARAMS.DAT file and running AUTOGEN with REBOOT. 


 
           ADD_NPAGEDYN       = 204800  ! change for DTA 
           ADD_SPTREQ         =  38000  ! change for DTA

Note
AFTER MAKING THESE PARAMETER CHANGES, YOU WILL NEED TO REBOOT YOUR SYSTEM IN ORDER FOR THEM TO TAKE EFFECT.

Chapter 3
Installing DTA

Note
Before installing DTA, make sure that you have read this manual COMPLETELY.

DTA can be installed on any:

The following items are included with this installation package:

3.1 License Registration

You should register and load the License PAK before you start the DTA installation.

To register a license under OpenVMS, first log on to the system manager's account, SYSTEM. You then have a choice of two ways to perform the registration:

  1. Invoke the SYS$UPDATE:VMSLICENSE.COM procedure. When it prompts you for information, respond with data from your License PAK.
  2. At the DCL prompt, enter the LICENSE REGISTER command with the appropriate qualifiers that correspond to License PAK information.

If you plan to use DTA on more than one node in a cluster, you will need to perform a license load on the other nodes after you complete this installation.

3.2 Install Instructions

To install DTA on your VAX or Alpha computer, you will need to work from a DEC VT100 or compatible terminal. Follow the steps listed below and type the commands shown. The VAX and Alpha systems are space conscious, so be sure to type the commands exactly as shown.

  1. MAKE SURE THAT YOU HAVE CHANGED THE SYSGEN PARAMETERS DESCRIBED IN Chapter 2, AND REBOOTED THE SYSTEM.
  2. Log on to the SYSTEM account: 


          Username:   SYSTEM 
      Password:  (enter your system password)

  3. Create the DTA directory: 


          $ CREATE/DIRECTORY SYS$SYSDEVICE:[TTI_DTA]

    Note
    DTA can be loaded into any directory on any disk ...e.g., $1$WORK:[DTA]

  4. Enter the DTA directory: 


          $ SET DEFAULT SYS$SYSDEVICE:[TTI_DTA]

  5. Verify that you are in the new directory. You should see the message "No files found." E.g., 


          $ DIRECTORY 
      No files found.

  6. Load instructions for CD-ROM:
    1. Put the DTA distribution CD-ROM into your computer's CD drive.
    2. Make the CD drive available. 


            $ ALLOCATE MKA0: 
      $ MOUNT MKA0:/OVERRIDE=ID 
      Volume is write locked 
      DTA mounted on _MKA0:

      Note
      MKA0 may have to be replaced with the appropriate CD identifier for your system.

    3. Transfer DTA to disk using OpenVMS BACKUP. 


            $ BACKUP/LOG MKA0:[DTA.KIT]*.*/SAVE *.*/NEW_VERSION 
      $ DISMOUNT MKA0: 
      $ DEALLOCATE MKA0:

      The transfer will take about 2 minutes. As DTA is transferred to disk, you will see a list of the files being transferred.

  7. Load instructions for tape:
    1. Put the DTA distribution tape on your computer's tape drive.
    2. Make the tape drive available. 


            $ ALLOCATE MSA0: 
      $ MOUNT MSA0:/FOREIGN 
      Volume is write locked 
      DTA mounted on _MSA0:

      Note
      MSA0 may have to be replaced with the appropriate magtape identifier for your system.

    3. Transfer DTA to disk using OpenVMS BACKUP. 


            $ BACKUP/LOG MSA0:DTA *.*/NEW_VERSION 
      $ DISMOUNT MSA0: 
      $ DEALLOCATE MSA0:

      The transfer will take about 2 minutes. As DTA is transferred to disk, you will see a list of the files being transferred.

  8. Activate DTA interactively by executing the following command:

    Note
    You must change your SYSGEN parameters before starting DTA. FAILURE TO MAKE THESE REQUIRED CHANGES WILL CAUSE THE DYNAMIC TAPE ACCELERATOR TO ABORT OR OTHERWISE FAIL. 


          $ @SYS$SYSDEVICE:[TTI_DTA]DTA_STARTUP

  9. Add the above command to your system startup command procedure. If you have a cluster, each member of the cluster that uses DTA must execute the DTA_STARTUP command. Adding the command to the system startup command procedure will cause DTA to start up each time the system is booted.
  10. DTA has now been installed on your computer.

Upgrading DTA
When upgrading to a new version of DTA, follow the same procedures you performed when you installed DTA for the first time.

If upgrading to an Alpha system, the update should be done at a time when you are planning a system reboot. On Alpha systems, device drivers cannot be reloaded. Your Alpha system must be rebooted to install the new DTA device driver. Upgrading DTA on a VAX does not require rebooting the system because device drivers can be reloaded on the VAX.

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