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VPARS

VPARS. Virtual Software Systems, Inc. http://www.vsoftsys.com/ Session 9155 SHARE in Orlando - February 2008. VPARS Introduction. VPARS: Virtual Private Active Record Shadowing

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VPARS

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  1. VPARS Virtual Software Systems, Inc. http://www.vsoftsys.com/ Session 9155 SHARE in Orlando - February 2008

  2. VPARS Introduction • VPARS: Virtual Private Active Record Shadowing • VPARS was developed in 1979-80 to provide a virtual test platform for the IBM TPF (Transaction Processing Facility) environment • VPARS is a software extension to VM that allows multiple guests to transparently share disks in a R/W mode

  3. VPARS DataBase • Records modified by each guest are maintained on its own private (or shared) VPARS database • Provides record isolation between guests that are sharing the disks

  4. VPARS Concepts (1 of 3) • Requires read-only links to the shared disks and read-write links to the VPARS database disk(s) • A write request is intercepted and the updated record is written to the user’s VPARS database. • Original record in the TPF base remains unchanged. • A different virtual machine can retrieve the original record from the TPF base, update it, and write it to its own VPARS database.

  5. VPARS Concepts (2 of 3) • When a read is issued for a record, VPARS searches its database directory. • If found, the record is returned from the VPARS database. Otherwise it is retrieved from the TPF base. • Whenever a record is modified and filed, it is written to the VPARS database. • A subsequent request for the same record will result in the record being retrieved from the VPARS database.

  6. VPARS Concepts (3 of 3) • The TPF system is not aware that VPARS is intercepting and handling its I/O requests. • Complete integrity of the TPF system is maintained because the records on the TPF base are never altered. • Therefore, several virtual machines can share a common TPF database under VPARS. • Each virtual machine will have its own VPARS database. • The number of virtual machines sharing a TPF database using VPARS is theoretically unlimited.

  7. VPARS Backups & Restores • Various functions of VPARS provide the ability to resume testing from any point, or to start with a clean VPARS database without affecting the shared TPF base. • Backup / Restore • Checkpoint • Clear (all or to a checkpoint)

  8. Benefits of VPARS • VPARS reduces the amount of hardware required to run multiple TPF test virtual machines. • Dedicated TPF disks are not required to run tests with different testing requirements. • The time required to refresh or restore a damaged TPF database is eliminated.

  9. TPF under z/VM without VPARS TPF 1 TPF 2 TPF 3 TPF 4 VM TPF database 100 – 2000 disks each TPFbase TPFbase TPFbase TPFbase

  10. TPF under z/VM with VPARS TPF 1 TPF 2 TPF 3 TPF 4 VPARS VM VPARS database 50 cyl - 256 disks each / TPF base 100 - 2000 disks VP DB VP DB VP DB VP DB TPF base

  11. Loosely-Coupled VPARS • All participating loosely-coupled TPF virtual machines write to the same VPARS database. • Each virtual machine must have write links to all disks in the database. • VPARS provides only the multi-write capability; record locking is the responsibility of the application. • IBM provides several facilities which can be used to provide record locking.

  12. Versatility of VPARS • In addition to TPF, VPARS can also service other operating systems such as Linux, running as guests under VM.

  13. Multi-level VPARS • Multi-level VPARS (or "concatenated") VPARS databases allow several databases to be searched for TPF input records. • The primary VPARS database is normally a read-write database. The rest are always read-only. Several users can share a read-only VPARS database. This may reduce the number of records required on each user's read-write VPARS database. • The primary database can also be a read-only database.

  14. VPARS Without a TPF Base • VPARS NOBASE provides an environment which requires significant space savings. No TPF base is required. • Accomplished by restoring only active TPF records to a VPARS database. Short term and unused long term pool records are not restored. • VPARS database can be shared by multilevel VPARS. • VPARS will not issue I/O requests against the TPF base except to retrieve IPL text. • A read of a record not found in the VPARS database will result in a zero record (binary zeroes) to be returned.

  15. Linux under z/VM without VPARS swap swap swap swap Linux 1 Linux 2 Linux 3 Linux 4 VM Linux database Linuxbase Linuxbase Linuxbase Linuxbase

  16. swap swap swap swap Linux under z/VM with VPARS Linux 1 Linux 2 Linux 3 Linux 4 VPARS VM VPARS database 50 cyl - 256 disks each / Linux database VP DB VP DB VP DB VP DB Linux base

  17. VPARS Internals VPARS Internals include the following components: • VM CP modules • Modifications to IBM VM CP modules • CMS modules • Modifications to IBM CP commands • CMS Execs for installation and maintenance • Documentation: product installation and user reference

  18. VPARS Virtual Software Systems, Inc. http://www.vsoftsys.com/

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