MV/Wiki

A Generation Ago

AOS/VS II

The contents of this page were copied from www.dg.com in 1997, it is thought they were written in 1993.

Features And Benefits

  • Dynamic, simultaneous support of timesharing and interactive user environments, multiple- batch job streams, and on-line applications
    • Provides significant flexibility to meet customer requirements
  • Sophisticated demand-paging, virtual memory management capability
    • Efficiently manages 4 GB logical address space
    • Supports up to 1 GB of physical memory
  • Fail-safe filesystem
    • Provides automatic recovery and eliminates filesystem failures through reliable fault- detection and failure-avoidance design
  • Easy-to-use, menu-driven file management utility
    • Reduces training time and costs
  • FSCOPY backup and recovery utility
    • Provides high performance, consistent backups of initialized LDUs
  • Disk mirroring, dynamic bad block remapping, dual-ported disk support, MRC support, and on- line fault isolation
    • Enhances system availability and reliability and speeds diagnostics and repair
  • Disk data caching
    • Improves performance through reduction in disk I/O
  • Compatibility across the 32-bit ECLIPSE MV/Family
    • Preserves investments in Data General systems through total application compatibility with [[software:aosvs|AOS/VS]]
  • Interoperability through resource sharing, network connectivity, and information exchange
    • Provides flexibility for use in multi-vendor environments including TCP/IP (UNIX), IBM Token Ring, Novell, Macintosh, OSI, and IBM mainframe

Data General’s AOS/VS II (Advanced Operating System/Virtual Storage II) is a sophisticated, multi-user, virtual memory operating system that supports the full range of ECLIPSE MV/Family computers and peripherals.

Featuring complete application compatibility with AOS/VS, AOS/VS II can be configured to handle a variety of user environments. During installation, the system manager tailors the operating system to the specific hardware configuration.

Other elements of AOS/VS II include an eight-level, process-protected ring structure; demand-paging, virtual memory management capabilities; multi-programming and multi-tasking techniques; and utilities to simplify program development and system management.

System Functionality

AOS/VS II resides in the highest-privileged rings (Rings 0 - 3) of the Data General ECLIPSE MV/Family architecture. User programs reside in the lower-privileged rings (Rings 4-7). AOS/VS II increases overall system reliability through its support of this eight-level, process-protected ring structure.

MV/Family systems protect the system software in inner rings by denying errant user programs in outer rings free access to the inner rings. This enables AOS/VS II to limit the system’s vulnerability to user programs.

Performance

AOS/VS II achieves superior performance through a variety of design features, including the virtual memory implementation. While physically protected by the ring structure, AOS/VS II resides in the same logical space as the user program, eliminating the context-switching overhead usually associated with user program actions.

Many communications products are integrated into the kernel of AOS/VS II eliminating extra process reschedules and data movement and allowing for controller sharing between protocols. These products include:

  • XTS II and DG/OTS which provide services for XODIAC, PC*I, and OSI products
  • AOS/VS II TCP/IP which provides TCP/IP protocol support
  • NetWare Transport for MV/Family systems which provides IPX/SPX protocol support
  • DG/NETBEUI which provides NetBEUI support

In addition, AOS/VS II can provide significant performance improvements through the data caching feature. This feature extends the buffer cache mechanism in AOS/VS II from system data to user data as well. Using a reserved cache of ten percent (10%) of system memory up to a maximum of 2 MB, reduction of disk I/O requests may be obtained.

Security

AOS/VS II provides a number of standard and optional security features. Standard features include username/password authentication at log on as wbility and higher availability.Optional features include password encryption and logging of all system activities.

An extensive set of user- and data-specific security features is also provided by AOS/VS II to protect data and resources from us dynamic bad block remapping. With the User Profile Editor utility, the system manager specifies user access priviledges and process restrictions. AOS/VS II EXEC checks the user profile for access privileges every time a user logs on to the system. Unauthorized access to, or alteration of data is controlled by the file access privileges assigned to the user.

AOS/VS II Release 3.01 has successfully completed its C2 evaluation and takes its place on the U.S. National Security Agency (NSA) Evaluated Product Listing. A system that is rated as being C2 Class provides a Trusted Computing Base (TCB) that implements user identification and authentication via username/password logon, discretionary access control (ACL) to protect user information, and auditing (REPORT) to enforce general user accountability. AOS/VS II is also participating in the NSA Rating Maintenance Program (RAMP).

Reliability And Availability

AOS/VS II Filesystem

The AOS/VS II filesystem provides fail-safe operation that results in improved reliability and higher availability. It speeds recovery, supports mirroring across any pair of disks, and provides dynamic bad block remapping. It offers an easy-to-use, menu-driven Disk Jockey filesystem management utility as well as complete application, tape-format, and XODIAC network compatibility.

The AOS/VS II filesystem offers quick recovery from catastrophic failures. Recovery time is simply the time required to re-start the operating system. In many cases, this is a matter of minutes. In a dual-ported disk environment, this capability is particularly important since the disks of the primary system become immediately usable to the backup system.

The AOS/VS II filesystem offers total application compatibility with AOS/VS. This includes system calls, error codes, and system management functions. If user applications have been properly coded, following Data General published guidelines, they will run without change on AOS/VS II.

MRC I/O Subsystem Support

AOS/VS II supports the MRC I/O subsystem. This subsystem represents a significant development in I/O capabilities and provides a high-speed, highly-reliable channel I/O interconnection that integrates MV/Family computers and disk and tape subsystems. The MRC design gives multiple AOS/VS-based MV/Family systems the capability to share the MRC subsystem as well as peripherals.

CLARiiON Support

AOS/VS II supports the CLARiiON disk array and tape array. The CLARiiON disk array offers high availability and uninterrupted data access. Every major component is fully redundant allowing for continuous operation through a single point of failure. Concurrent RAID levels 0, 1, 3, and 5 are supported so users can optimize AOS/VS II performance for their applications.

Delivering higher performance capabilities than conventional tape drives, the CLARiiON tape array provides unattended backups and restores. By striping the data and parity information over multiple drives in parallel, the backup or restore operation can continue in the event of a single drive or tape failure.

Both the disk array and tape array can be connected to an MRC subsystem which adds auto reroute functionality.

Disk Mirroring

Disk mirroring lets the system manager effectively maintain two identical copies of data across any pair of logical disks. Through the use of mirrored disks, AOS/VS II provides automatic recoverability from failure without application disruption or data corruption. By mirroring data on two redundant paths, AOS/VS II automatically reverts to the second set of data, should any component in the path to either set of data fail.

Dynamic Bad Block Remapping

Used in conjunction with disk mirroring, AOS/VS II can correct bad blocks that appear on the disk. When AOS/VS II detects a bad block, it will read from the mirrored image automatically to obtain the correct data, returning that to the user application. Then the AOS/VS II filesystem will remap the bad block to a known good location and write the correct data to the disk. In this way, it is possible for the filesystem to correct disk-read failures.

Dual-ported Disk Support

Dual-ported disk support lets AOS/VS II users attach one or more disk units between two MV/Family systems. The primary advantage to dual porting is fast recovery and access to data if one system fails. By physically attaching the same disk drive to controllers in two different MV/Family systems, and configuring AOS/VS II on both systems to use the disk, the user can make the same disk available to either system. Upon detection of a system failure, the operator can easily request the other system to start using the failed system’s disks. Recovery time is simply the time required for the operator to detect the failure and initiate recovery.

Repair Under Power

AOS/VS II supports the repair-under-power features of the MRC. When used in combination with Data General on-line diagnostics capabilities, it is possible to physically remove failed system components and replace them with working units. While the component is under repair, AOS/VS II will suspend any outstanding I/O to that device. The outstanding I/O can be aborted, allowing the application to invoke specific recovery procedures or other alternatives.

On-line Diagnostics

AOS/VS II supports the on-line fault isolation and diagnosis features of the MRC when used in combination with the Data General on-line diagnostic subsystem. This capability allows nodes and specific peripherals on the MRC subsystem to be tested while AOS/VS II is operational.

On-line diagnostics, together with the repair-under-power features of the MRC subsystem, provide a very powerful, high-availability capability to AOS/VS II.

Automatic Reroute

AOS/VS II supports auto-reroute around component failure when multiple paths exist. In MRC configurations, there may be enough hardware to allow for multiple I/O paths to disks. AOS/VS II will automatically switch the I/O to use the best secondary route (the one with the least hardware in common with the primary route) without any application failure or breaking of disk mirrors. After the failed component is replaced, the operator can dynamically switch back to the initial primary route.

Automatic Reboot

Due to the fact that there is no need to run FIXUP after a system failure, AOS/VS II supports an auto- reboot option. This option allows the system to come back up (and restart applications) with no operator intervention. Auto-reboot is available on all MV/Family processors. In addition, the MV/40000 HA and MV/60000 HA systems will initiate the auto-reboot after de-configuring faulty hardware.

Internal System Management Features

Multi-programming and Multi-tasking

AOS/VS II is a process-oriented, multi-programming operating system. A process is a collection of program steps – a sequence of instructions – sharing up to 512 MB of address space. Each process is assigned a set of resources and privileges that determines how much time and memory the process can use. AOS/VS II supports up to 32 tasks per process. The operating system multi-tasking feature controls the concurrent execution of multiple tasks through a single process and provides efficient handling of multiple asynchronous events within a single-user program.

Scheduling

Process scheduling is determined by process priority and eligibility states. Users can assign process priorities from 1 to 511. The priority will determine where among three groups the process will be assigned and consequently its scheduling characteristics. Two of the groups use round-robin scheduling and the third group uses heuristic scheduling. The priorities within these three groups can be varied to suit the user’s application environment needs.

Intertask and Interprocess Communications

AOS/VS II allows processes to communicate using multiple, free-format messages of variable length. Processes send and receive messages using full-duplex communications ports. Processes sending messages can continue activity without delay. If a receiver is not waiting for the message, AOS/VS II can spool the message. Conversely, the operating system can suspend a task to receive a message.

Demand Paging

The virtual storage design provides each application program with up to a 512-MB address range. Demand paging separates a user’s logical program addresses into 2-KB pages. Not all pages of a program’s logical addresses need to be active in memory at the same time. As program execution flow changes over time, AOS/VS II demand paging keeps only the active pages that comprise a program’s working set in memory. Non-active pages are kept on disk, ready to be moved into memory when required.

System Utilities

AOS/VS II provides a number of utilities to simplify program development and system management.

Disk Jockey (DJ) is an easy-to-use, menu-driven utility that creates and manages logical disks. It runs both as a process of AOS/VS II and as a standalone program. DJ provides six basic functions: formatting physical disk units; formatting logical disk units; installing system software and microcode on a logical disk; copying logical disks (disk-to-disk and disk-to-tape); defining the default operating system microcode on a logical disk; and providing a diagnostic function that lets the system manager verify that the logical disk and file structure is correct.

When DJ is used to boot AOS/VS II, the Disk Jockey Autosizer automatically creates a device- configuration table. This table is available to system utilities to determine the system configuration at boot time. For the inexperienced system manager or for configurations unknown to the user, DJ Autosizer reduces the amount of detail required to make configuration changes.

The VSGEN system configuration-validation interface is consistent with DJ and System Manager Interface (SMI) and is upwardly compatible with the previous implementation of VSGEN. It provides three system configuration validation levels and offers several features. When a device is created, the user specifies any name desired for the device as well as device attributes, such as device code, type, and number of units. All further references to that device are then made with the name the user provided.

FSCOPY is an AOS/VS II backup and recovery utility that is optimized to work with large disks, including disk arrays and tape arrays. FSCOPY does consistent image backups of initialized LDUs. When FSCOPY starts, it takes a snapshot of the LDU. Applications can be restarted during the backup. Either entire LDUs or specific files on the LDU can be restored.

Interoperability

AOS/VS II is a key component of system interoperability in today’s open systems environment. A number of services provide standard resource sharing, network connectivity, and information exchange.

Resource sharing includes system-provided services which facilitate access to media interchange, file transfer, file sharing, remote print, tape, and batch services, naming services, and virtual terminal.

Network connectivity defines the underlying network itself by describing the protocols and topologies used such as protocols, link type, application programmer interfaces (APIs), and network management.

The highest level of interoperability is information exchange. It offers application-provided services which allow the user to exchange forms of information through electronic mail, remote databases, and distributed applications.

Kernel-based terminal connectivity options of AOS/VS II also enhance the interoperability features of the ECLIPSE MV/Family of systems as follows:

  • Full screen Telnet support allows a user on a UNIX system to remotely log on to an AOS/VS II system and start running screen-based applications
  • AOS/VS II also supports VT-compatible terminals; any application that uses a DASHERR D200 can utilize a VT-compatible terminal or terminal emulator transparently
  • The AOS/VS II XODIAC VCON server has been moved into the kernel to provide better performance by eliminating extra process reschedules, data movement, and inter-processing communications
  • AOS/VS II supports PAD terminal connections, the X.29 protocol for PAD, and the X.3 protocol for setting PAD parameters
  • The CS2000 and CS2100 terminal servers are supported by AOS/VS II using both the XNS and TCP/IP protocols
  • Support for Novell Virtual Terminal (NVT) has also been integrated into the AOS/VS II kernel
  • VS caller ID allows a programmatic way for applications to determine the address for network- based terminal connections

Optional Performance Tools And Utilities

Performance Monitoring and Tuning

The Data General Systems Evaluation and Performance Analysis Center (SEPAC) offers a full range of services to help users gain maximum performance from their MV/Family systems and AOS/VS II. Services include MV/Checkup, Stats-Only, Off-Site Performance Analysis Report, Enhanced On-Site, Stats Plus On-Site, Baseline Capacity Analysis, and VSPAC/ONE.

Specific to AOS/VS II, VSPAC/ONE lets users establish their own in-house AOS/VS Performance Analysis Center. VSPAC/ONE provides a detailed method of system performance data collection, reporting, and interactive analysis. It offers a proven, cost-effective system management tool to help perform system audits, establish and track utilization trends, prevent performance crises, and optimize hardware or software configurations.

The AOS/VS II Performance Package

The AOS/VS II Performance Package is a set of utility programs that can help users analyze AOS/VS II system performance. The main system performance utility, MONITOR, gathers, displays, lists, and logs system-wide statistics.

The MONITOR Screenfile Generator creates screens containing disk unit, memory, CPU, and PMGR statistics, as well as screens displaying terminal controller engine and console line statistics.

Load 3/Dump 3

The AOS/VS LOAD 3/DUMP 3 backup utility is a fast, reliable, and easy-to-use file backup (dump) and recovery (load) program that features improved reliability, flexibility, and performance. It is compatible with other Data General backup utilities and can recover files backed up by AOS/VS DUMP, DUMP II, or DUMP 3, and can bypass problems that would stop LOAD and LOAD II.

Supported Software

The accompanying chart provides an overview of the Data General development languages, development tools and utilities, data management software, decision support and presentation graphics, and communications products supported by the AOS/VS II operating system. For a more complete description, please refer to the respective product literature.

Application Development Languages:

COBOL, BASIC, PL/1, FORTRAN 77, Pascal, ADA, RPG II, C, Business BASIC, Common LISP, ICOBOL

Software Development Tools and Utilities:

CCA/EMACS Editor, SGU Screen Generator, SORT/MERGE Utility, SWAT Source Language Debugger, SMU Source Management Utilities, LOAD 3/DUMP 3, Performance Monitor, Clasp, MV Data Center Manager

Data Management Software:

DG/DBMS, INFOS II, DG/SQL, DG/Data Dictionary, DG/INGRES, INFOS II, FC

Communications:

XODIAC, XTS II, AOS/VS SNA/RJE, AOS/VS DG/SDLC, AOS/VS II TCP/IP, DG/OTS, DG/STAM, XDLC/QLLC, AOS/VS SNA/3270, XCOM 6.2, AOS/VS II ONC/NFS, AOS/VS RJE80, DG/X.400, DG/NETBEUI, NetWare Transport for MV, NetWare Services for MV, AOS/VS RCX70, AOS/VS HASP II, DG/SNA

Office Automation Services:

CEO, CEO Object Office, CEO Connection/PC, Forest & Trees, CEO/DXA, CEO PXA/SNA