SOFTWARE DESIGN FOR X - Software Design for Six-Sigma: A Roadmap for Excellence - page 376

TABLE 14.5 Best-In-Class Defect Removal Efficiency

“Best in Class”

Application Type Defect Removal Efficiency

Outsourced software 92%

IT software 73%

Commercial software 90%

System software 94%

Military software 96%

Web software 72%

Embedded software 95%

measuring phase containment of defects, measurements can be collected to show the
separation between defect insertion and discovery phases. 16

14.2.4.1 DFSS Identify Phase DFR Practices. The requirements for soft-
ware reliability are to: identify important software functionality, including essential,
critical, and nonessential; explicitly define acceptable software failure rates; and spec-
ify any behavior that impacts software availability (see Section 14.3). We must define
acceptable durations for software upgrades, reboots, and restarts, and we must define
any operating cycles that apply to the system and the software to define opportu-
nity for software restarts or rejuvenation such as maintenance or diagnostic periods,
off-line periods, and shutdown periods.
In this identity, conceptualize, optimize, and verify/validate (ICOV) DFSS phase,
the software team should define system-level reliability and availability software
goals, which are different from hardware goals. These goals become part of the
project reliability and integration plan and are applied to the conceptualize and
optimize phases. The two major activities in this phase are:

Software reliability goal setting
Software reliability program and integration plan

14.2.4.2 DFSS Conceptualize Phase DFR Practices. The reliability engi-
neering activity should be an ongoing process starting at the conceptualize phase of a
DFSS-design project and continuing throughout all phases of a device life cycle. The
goal always needs to be to identify potential reliability problems as early as possible
in the device life cycle. Although it may never be too late to improve the reliability
of software, changes to a design are orders of magnitude less expensive in the early
part of a design phase rather than once the product is released.
A reliability prediction can be performed in the conceptualize DFSS phase to
“ballpark” the expected reliability of the software. A reliability prediction is simply

16 See Silverman and De La Fuente, http://www.opsalacarte.com/pdfs/Tech Papers/Software Design for
Reliability - Paper.pdf.