2. USAGE GUIDELINES › 2.2 VTS Component Usage Guidelines › 2.2.2 Virtual Tape Performance Analysis › 2.2.2.1 IBM VTS Virtual Tape Performance

2.2.2.1 IBM VTS Virtual Tape Performance

IBM VTS employs a number of strategies to ensure that the
VTS-managed DASD cache maintains a sufficient percentage of
free space to support the creation of new virtual tape
volumes and to accommodate the loading and access of existing
volumes from the stacked tape cartridges that serve as the
real media repository for virtual tape volumes and data sets.
 
Refer to IBM VTS documentation for specific measurement
thresholds that indicate performance degradation.  For
example, there may be a specific IBM VTS guideline that
specifies that, on an hourly basis, the average time to
satisfy virtual volume mount requests should not exceed 30
seconds.
 
Vendor-suggested guidelines can be compared to actual
performance using the VTS component files as follows:
 
o VTS Distributed Library Activity (IVTVDL) file
 
  The IVTVDL file provides overall VTS-level performance data
  for each distributed VTS.  The type of distributed VTS is
  identified with the VTS Type (IVTTYPE) data element, and
  includes STANDALONE, UI, and SECONDARY.  This file
  provides the following statistics:
 
  - Physical tape drive and physical mount statistics
  - Physical cartridge utilization statistics
  - Virtual tape drive and virtual mount statistics
  - Virtual volume statistics
  - Overall cache utilization statistics
  - Throttling and data compression statistics
  - z/OS host read and write data blocksize statistics
  - Overall cache and physical volume capacity and usage
 
o VTS Composite Library Activity (IVTVCL) file
 
  The IVTVCL file provides VTS performance data for the
  COMPOSITE VTS in a peer-to-peer configuration.  This file
  provides the following statistics:
 
  - Virtual tape drive and virtual mount statistics
  - Virtual volume statistics
  - z/OS host data compression statistics
  - z/OS host read and write data blocksize statistics
 
o VTS VTC Controller Detail (IVTVTC) file
 
  The IVTVTC file provides information for each virtual tape
  controller used by the COMPOSITE VTS in a peer-to-peer
  configuration.  For each virtual tape controller, this file
  provides the following statistics:
 
  - Virtual tape drive and virtual mount statistics
  - Virtual volume statistics
  - Virtual volume copy statistics
  - z/OS host data compression statistics
  - Virtual controller management settings
 
o VTS Cache Usage Preference Level (IVTVCU) file
 
  The IVTVCU file provides information for each cache
  preference level used by the VTS. Cache preference levels
  are used to separate virtual volumes into groups with
  different management objectives.  For each preference
  level, data element Cache Usage Preference Level ID
  (IVTCUPL), the file provides:
 
  - Virtual volume migration activity
  - Virtual volume age-in-cache statistics
  - Cache hit mount statistics
  - Cache miss mount statistics
  - Fast ready mount statistics
 
o VTS Physical Drive Activity (IVTPTU) file
 
  The IVTPTU file provides information for each individual
  tape drive type (up to 2) used by a VTS in an IBM
  self-managed tape library.  For each device type, data
  element Physical Tape Drive Device Class (IVTDCI), the file
  provides:
 
  - Physical tape drive and physical mount statistics
  - Data volumes written to primary and secondary pools
 
o VTS Volume Pool Statistics (IVTVPS) file
 
  The IVTVPS file provides information on physical cartridges
  at the volume pool level.  For each Volume Pool Identifier
  (IVTVPN), the file provides:
 
  - Volume pool cartridge media types
  - Counts of scratch and active volumes by media type
  - Information about volumes borrowed from other pools
  - Cartridge use percentage buckets
  - Ages of logical volumes on cartridges
  - Volume pool management policy settings
 
o VTS Tape Library Config and Activity (IVTTCA) file
 
  The IVTTCA file provides information about the physical
  tape drives and mount activity in the self-managed tape
  library used by the VTS.  The file provides:
 
  - Physical tape drive configuration information
  - Physical tape drive activity statistics by category:
    Mounts, Demounts, Ejects, Audits, and Inserts
 
o VTS Import/Export Statistics (IVTIEX) file
 
  The IVTIEX file provides information about physical
  cartridges imported and exported from the self-managed
  tape library. The file provides:
 
  - Counts of physical cartridges imported and exported
  - Counts of logical volumes on the physical cartridges
  - Data volume involved in the imports and exports