IS Cutover Approaches
Immediate (direct)
The old system stops running and the new system begins at a specific
point in time.
Advantages
Fastest return on investment
No duplication of efforts or costs
No confusion, only one system running at a time
Forces users to commit to new system
Disadvantages
Nothing to fall back on if failure
Nothing to compare new system results to
All training must be done at once
IS must do all "fixes" in a short period of time
Users often resist
Used
For most small systems, most upgrades, highly integrated large
systems with significant on-line components.
Phased by location
The new system is installed one at a time, or in small groups,
across similar separate locations. Within each location, the cutover is immediate.
Advantages
- Risk limited to one location at a time
If it goes well in early units, later units will support
May be able to spread out costs, particularly for new hardware
Spreads out training effort, smaller training group needed
IS can make "fixes" in a planned manner
Disadvantages
- Delays return and benefits
Just because it works in one unit, doesn't mean it will work in later ones
If early units are failures, later units will strongly resist
Different units on different systems can cause confusion
At a higher level, both old & new system results must be combined
Nothing to compare new system results to
Only useful in situations where similar units exist
Used
For larger on-line systems where similar units exist (such as retail
bank locations). Start with simplest and smallest units first and move to larger, more
complex units.
Phased by function
Modules (functions) of the system are installed one at a time.
Usually starts with modules with greatest data entry and then follows data.
Advantages
- Works in environments where phased by location won't
Can reduce risk
Spreads out training costs
Spreads out IS fixes
Only one system running in each module
Disadvantages
- Delays return and benefits
Often complex and confusing
Need method to transfer data from a new module to old modules
Bad data from new module usually can corrupt old modules
Nothing to compare new system results to
Used
For larger on-line systems where phased by location is practical.
Parallel
New system is started while old system is continued. Both old and
new run simultaneously until there is confidence in new system.
Advantages
- Reduces risk, old system available to fall back on
Less resistance initially
Have results of old system to check new against
Spreads out training costs
Spreads out IS fixes
Disadvantages
- Delays return and benefits
- Two systems in same departments are very confusing
Users forget training each time go back to old system
High level of complaints and actual resistance to new system
Extremely costly to run two systems
Need to hire additional staff during parallel period
Not practical or impossible with on-line systems
Used
For larger batch systems.
- R. S. Kulzick – 11/07/01 -
Contact rkulzick@stu.edu with
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Copyright © 2001 Raymond S. Kulzick - Last modified: September 13, 2008