Estimating resource requirements is more of an art than a science.
Although rules of thumb and generalized algorithms are useful, each
installation’s needs and environment are unique. To optimize the
estimating effort, each planning team should allow a reasonable margin
of error and be alert to the subtle interactions that can affect performance,
throughput, and resource requirements. The following comments are
included to stimulate your analysis during the estimation process:
- Object size and activity level influences virtually all aspects
of resource utilization. The validity of the remaining resource estimates
depends on the accuracy of these fundamental assumptions.
- When estimating object transfer rate and other throughput issues,
remember that OAM is part of a complex system, influenced by many
factors.
- Application design can have a significant effect on OAM efficiency.
For example, careful use of buffering can reduce virtual storage requirements.
- When estimating the amount of time needed to complete a storage
management cycle, consider the following:
- All data movement resulting from storage class changes, whether
caused by class transition or application request, is handled during
the storage management cycle.
- Movement from disk to optical or tape is typically faster than
the reverse.
- The frequency and volume of backup copies of objects that are
made during the cycle can increase processing time.
- The effective drive transfer rate is faster for a single large
object than for multiple small objects.
- In addition to estimating obvious needs, such as DASD, tape, and
optical storage space, consider possible requirements for resources
that are less directly related to the OAM installation. For example,
do you have enough of the following:
- Trained support personnel, application developers, and end users?
- User IDs with the correct access authority?
- Tapes to process backups for the DB2 tables?
- Shelf space for shelf-resident optical disks and library-resident
tape volumes associated with manual tape libraries?
- Shelf space for shelf-resident tape volumes used with stand-alone
tape devices?
- Customized transport classes (CTCs) for OAM XCF processing to
decrease any possible impact on cross-system processing based on locality
of hardware versus the system originating the request.
- DB2 threads and locks to process concurrent access to tables during
an OSMC cycle?