RemoteSHADOW OpenVMS -Data Replication Data Recovery

The Disk Mirroring system for OpenVMS allows a VMS System Manager to maintain redundant databases for the survival of media failures.

A shadow set consists of a master-disk device and one or more members. User applications issue I/O operations to the master disk, which is a Files-11-mounted device. Write operations are performed for all available members within the set and Read operations are balanced. An additional feature allows a user to specify a preferred drive for reading.

SHADOW offers an automatic and transparent rollover on a member failure within the shadow set. As long as a single member within the set remains available for I/O operations, RemoteSHADOW does not pass back any notification of the failure to the user program. All modifications to shadow-set status are logged to the operator console and journaled to a disk file for audit purposes. When a hardware error is detected on a set, that device is "removed".

SHADOW offers users the ability to create and/or delete shadow sets and to add, modify, and/or remove a member with no interruption or loss of service. When you want to add a member, RemoteSHADOW offers an optimized, on-line-disk copy facility to ensure that all volumes reflect the same data. This on-line copy is further optimized by selectively copying only those sectors which have been allocated under the Files-11 structure.

The user-interface program is invoked in the DCL-command style with qualifiers and parameters for program input. RemoteSHADOW uses the normal VMS privileges required for manipulating disk volumes.

The MONITOR program uses a windows-oriented approach to display shadow-set information on one or more nodes within the DECnet network. MONITOR also allows the entry of commands for your additional convenience.

FileSHADOW Option:


Data Replication and Data Recovery for OpenVMS The FileSHADOW Option provides the added capabilities of: Shadowing selected critical files, and Shadowing dissimilar (heterogenous) disks.

Shadowing selected files can significantly reduce the overall disk storage requirements which other systems can consume. A performance enhancement can also be realized since read I/O's are balanced and only the critical files you designate have their write I/O's mirrored. To shadow one or more critical files, you create a virtual disk of specified size, into which you place your files. This virtual disk can then be shadowed to either a real physical disk or another virtual disk. Shadowing a physical disk to a virtual disk is the underlying concept behind dissimilar support. The real disk may be an RZ26 while the virtual disk resides on the unused portion of an RZ28. This allows an RZ26 to be shadowed to a portion of an RZ28, and the remaining free space can be used for any other purpose.

The FileSHADOW option is a layered product of SHADOW and is separately priced.

RemoteSHADOW Option:


Data Replication and Data Recovery for OpenVMS With the RemoteSHADOW Option(RSO), the strategy for coping with media failures can be expanded to include local-site failures. The RemoteSHADOW Option provides the capability for continuing access to and availability of your data, even when your local-computer site is down. This option means that your high-availability applications can continue to operate from a contingency site using todays data. The RemoteSHADOW Option allows a VMS System Manager to designate one or more shadow-set members as remote volumes. RSO uses a high-speed network for remote communications and supports the concept of out-of-sync tolerance. When a shadow set specifies no out-of-sync tolerance, all Write operations must complete on local and remote systems together. In this manner both the local and remote systems are in synchronization. When the disk I/O traffic and rates exceed the network-communications throughput, a set may specify an out-of-sync tolerance. Specified in time (seconds), an out-of-sync tolerance means that insufficient network bandwidth should not impact the local system and that the remote system is to be updated asynchronously after the local system. Thus, the local and remote systems can be out of synchronization. The maximum out-of-sync tolerance is user-specifiable. For example, 600 seconds would allow a remote system to be a maximum of ten (10) minutes behind a local system. RSO does endeavor to stay in-sync as much as is possible. All Read operations are performed from faster local drives, regardless of out-of-sync tolerance.

The RemoteSHADOW Option also provides a communications-network-restart feature that allows a recovery from temporary-network failures without the need for a volume catchup.

For improved-network utilization, RSO provides a data-compression feature that, depending upon user data, can significantly reduce the raw amount of transmitted data. RSO also supports a network-data-encryption feature that, when enabled, encrypts all transmitted and/or received data. This feature ensures that your proprietary and sensitive data never becomes viewable over a communication line.

The RemoteSHADOW option is a layered product of SHADOW and is separately priced. (The FileSHADOW Option is included with the RemoteSHADOW Option).

Minimum Hardware Supported:


This product requires a valid OpenVMS configuration. It is warranted for use with Digital's MASSBUS, UNIBUS, QBUS, DSA, DSSI, BI, XMI and SCSI disks, used in conjunction with any Digital-disk controller.

SHADOW fully supports the VMScluster environment and also works with all third-party controllers and disk drives that use unmodified, Digital disk-device drivers.

Prerequisite Software:


SHADOW V2.6 runs on any OpenVMS processor, using VMS VAX Version 5.5-2 or later, or OpenVMS Alpha V6.1 or later. For execution within a VMScluster, ASCI highly recommends an OpenVMS DECnet Full-Function license.

The RemoteSHADOW Option supports OpenVMS DECnet and/or TCP-IP.

Optional Software:


The FileSHADOW Option as described in this Software Product Description.

The RemoteSHADOW Option as described in this Software Product Description.

VIRTUOSO Virtual Disk and Disk Caching system can be combined with SHADOW to allow the shadowing of partial, rather than full volumes. VIRTUOSO also provides Data Caching, Disk Striping, Encryption and other features that improve the performance, reliability, and security of disk data.

Software Installation:


Installation of this product is subject to the terms of the ASCI Standard Software Product License Agreement. SHADOW is designed to be Customer installable and uses Digital's VMSINSTAL facility.

Warranty Information:


This software is sold through ASCI's Software Product License Agreement which warrants the product for ninety (90) days from the date of purchase. Warranty services include telephone-remedial support and product upgrades.

Customer Support Information:


After the initial product warranty expires, ASCI offers a twelve-month customer support plan. This includes remedial support, product upgrades as they become available. The annual customer support plan is separately priced.

Ordering Information:


ASCI normally distributes all material via CD-ROM. However, ASCI honors requests for other magnetic media for a minimal charge, but you must indicate these in your letter and/or purchase order. The current prices are available upon request. Multi-CPU and Educational-Institution discounts are available.

This software is licensed under Digital's License Management Facility (LMF). A Product Authorization Key (PAK) is required prior to product installation and execution.

SHADOW consists of a CD-ROM distribution of software (1), User's Manual (1), Software Product License Agreement, Software Product Description, and Warranty Registration Certificate.

The RemoteSHADOW Option consists of a CD-ROM distribution of software (1) and Addendum (1).

SHA_150_LIC-License and Distribution Media
SHA_151_LIC-RemoteSHADOW Option License and Distribution Media
SHA_152_LIC-FileSHADOW Option License and Distribution Media
SHA_150_RTC-SHADOW-Right-to-Copy License
SHA_151_RTC-RemoteSHADOW Option Right-to-Copy License
SHA_152_RTC-FileSHADOW Option Right-to-Copy License
AD_150_SHA-User's Guide


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