The Virtual Software Systems' products presented here are mainframe software and require the IBM z/VM operating system running at first level.
VPARS is a software enhancement to z/VM that allows multiple virtual machines to transparently share a TPF (Transaction Processing facilty) database. Although the TPF records that are modified are maintained on a VPARS database, it appears to each TPF system that it is actually writing to the TPF base. This provides record isolation between virtual machines that are sharing a TPF system. All levels of TPF are supported by VPARS.
Multi-level (or "concatenated") VPARS databases allow several VPARS 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, since a shortload or longload (or any other data) can be written to a database which is then shared read-only among several VPARS users. The primary database can also be a read-only database.
ShadowDisk/Z is a software enhancement to z/VM that allows multiple virtual machines to transparently share a z/Linux filesystem. Although the filesystem records that are modified are maintained on a VDISK database, it appears to each z/Linux system that it is actually writing to the underlying filesystem. Both RedHat and Novell SuSE z/Linux systems are supported by ShadowDisk/Z.
Multi-level (or "concatenated") VDISK databases allow several VDISK databases to be searched for z/Linux filesystem blocks. The primary VDISK database is normally a read-write database. The rest are always read-only. Several users can share a read-only VDISK database. This may reduce the number of records required on each user's read/write VDISK database, since data written to each database can be shared read-only among several VDISK users. The primary database can also be a read-only database.
VTAPE (Virtual Tape)
VTAPE is an implementation of a virtual tape device in z/VM software. All defined virtual tape drives are seen as real attached tape devices to guest machines. VTAPE implements a database technology that intercepts tape block reads and writes, and performs the corresponding operations against the database in a manner which is transparent to the guest, and which is seen as normal tape I/O activity by that guest. This approach offers the following benefits to the installation:
Users can define and the use many more virtual tape devices than the number of real tape devices available in the shop, thus eliminating the need to buy more real devices.
Tape mounts are satisfied without operator intervention – no operator bottlenecks.
Developers can test tape-based applications without tying up real devices. Guest machines, such as z/OS and z/VSE, can backup data to tape faster and more efficiently than with real devices.
The use of virtual tape eliminates the need for JCL tape-to-disk conversions in z/OS and z/VSE shops.
Since all virtual tapes actually reside in a disk VTAPE library, the library can be backed up and restored via VSSI utilities, allowing for more efficient restoration during Disaster Recovery testing and use.
Virtual Tape is not a tape management system, but a complete implementation of tape drives and tapes in software.