Parallel conversion. ′parə‚lel kən′vərzhən (computer science) The process of transferring operations from one computer system to another, during which both systems are run together for a period of time to ensure that they are producing identical results.
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Updated September 26, 2017
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- Parallel Conversion 1 Definition A project implementation technique in which an existing system is run in parallel with the new system, with the comparison of operations and results to verify that the new system will properly replace the functions of the old.
- Serial-to-parallel conversion: Conversion of a stream of data elements received in time sequence, i.e., one at a time, into a data stream consisting of multiple data elements transmitted simultaneously.
- A parallel conversion is one in which both the old and new computer systems are operated simultaneously. This is usually done to keep the old system available as a backup until the new system is working satisfactorily.
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Updated September 26, 2017
Conversion from one computer system to another can be accomplished by several methods. A parallel conversion is one in which both the old and new computer systems are operated simultaneously. This is usually done to keep the old system available as a backup until the new system is working satisfactorily. Parallel conversion boasts some advantages, but it also has some drawbacks as well.
Running Two Systems Simultaneously
Running two systems in parallel demands twice the resources to accomplish the same work as a single system. This demands more electricity and increases operating costs. Workers must also perform twice their normal work load in order to achieve the same output, essentially entering or changing data twice for every one time they would do so on a single system to ensure that information remains identical between both. The doubled workload slows production, which raises the cost of the final product by diminishing the workers' potential output per paid period of work.
Probability of Errors
Input errors are always a possibility, but when the amount of data being input doubles, the probability of an error increases with it. The likelihood of errors may also increase if workers are compelled to work faster, and an input error on one system will take it out of synchronization with the other. When this happens, the systems are no longer parallel, and further time and energy must be invested to track and correct the erroneous entry.
Advantages of Parallel Conversion
While parallel conversion does have some disadvantages, its primary appeal is in the potential for continued smooth operations during the changeover period. The new system can be run alongside the old system for weeks or months, allowing the discovery of any problems in the new system without exposing the business to a shutdown when problems occur. This feature is especially useful when adopting new untested systems or systems that may require unforeseen specialization and optimization after implementation.
Alternative Conversion Strategies
In addition to parallel conversion, several other conversion strategies exist. An abrupt cutover, also known as a plunge, involves shutting down the old system and converting to the new one at a predetermined time. Abrupt conversions are typically scheduled during extended periods of down time, such as weekends or the beginning of a new financial year, in order to discover and correct any potential problems before workers return and begin using the new system. A location conversion occurs when several locations use the same system. One location becomes a test site for the new system and, when the problems are worked out there, the system is implemented at all other locations as well. A staged conversion involves implementation of updates or a new system in stages, with each stage being debugged before the next is implemented.
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Parallel adoption is a method for transferring between a previous (IT) system to a target (IT) system in an organization. In order to reduce risk, the old and new system run simultaneously for some period of time after which, if the criteria for the new system are met, the old system is disabled. The process requires careful planning and control and a significant investment in labor hours.
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Overview[edit]
This entry focuses on the generic process of parallel adoption; (real-world) examples are used for a more meaningful interpretation of the process if necessary. Moreover a process-data model is used for visualizing the process which is intended to provide a complete overview of all the steps involved in the parallel adoption, but emphasis will be laid on the unique characteristics of parallel adoption. Some common characteristics, especially defining an implementation strategy, that go for all four generic kinds of adoption are described in Adoption (software implementation).
Other kinds of adoption[edit]
Besides parallel adoption, three other generic kinds of adoption can be identified. The choice for a specific adoption method depends on the organizational characteristics; more insight on this topic will be provided below. The three other adoption methods are:Product Software Adoption: Big Bang Adoption (Also known as Direct Conversion, slam dunk, or cold-turkey strategy), Phased adoption and Pilot adoption.
Parallel Conversion Definition Chart
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- Product Software Adoption: Big Bang Adoption/Plunge Adoption: A big-bang adoption entails transferring the entire organization from the old system to the new system in an instant changeover. This is the cheapest option but if the new System fails, the organization is in big trouble. It also opens risks for the system not to be accepted by its users. However, this may be the only approach to take when the two systems can not coexist or activating the new system is an emergency.
- Phased adoption (Also known as gradual conversion): In phased adoption implementation, the organization is gradually transferring to a new system in different phases, per module or sub-system. Some systems are incapable of being introduced in pieces as it is too reliant on the whole system. Using the phased adoption has less risks, but causes the most disruptions due to it taking the most time to transfer from the old system to the new.
- Pilot adoption: The pilot adoption method is used for large organizations that have multiple locations or largely independent departments. The new system is introduced in one of the locations or departments and extended to other locations or departments over time. (limited boundary if a new system is a failure) (Turban, 2002)
There are several instances when parallel conversion can not be considered a viable conversion strategy. First consider if the new system contains significant schema changes. Data elements required by one system that are not being populated by the other can lead to at best data inaccuracies and at worst data corruption. Another concern is if the system relies on consumer off the shelf technology (COTS). If a COTS vendor's documentation states that more than one application can not share the same database, then parallel conversion is not an option. An example would be Oracle's Siebel products. Other COTS products may also place restrictions when patches or major upgrades require unique license keys. Once applied they may make database changes that might cause the application to falsely detect a parallel system running against the same database as an attempt at getting around licensing controls and thereby disable the system.
Place in implementation process[edit]
There seem to be little conventions regarding the process of parallel adoption. Several sources (e.g.: Turban, 2002, Eason, 1988, Rooijmans, 2003, Brown, 1999), do not use a single process-description name. The term parallel adoption is denoted in these sources, although consistent per source as: parallel conversion, parallel running, shadow-running, parallel cutover and parallel implementation. This appears to be the case because a generic description of the process does not need a distinct classification. There are a quite some standard implementation methods, where different adoption techniques are described but often in a practical context; real-world case scenario or a more comprehensive set of implementation techniques like Regatta: adoption method, SIM and PRINCE2. In general, parallel adoption can best be seen as a Systems Engineering method of implementation of a new system.
In principle, the parallel adoption method is different from the decision to change a system in an organization and can be seen as one possible mean to achieve that goal. However, there are quite some factors that are being taken into account in determining the best implementation strategy. Moreover, a successful implementation can depend to a big extent on the adoption method. (Lee, 2004)
The process[edit]
The parallel adoption process can not be represented without paying attention to the steps before the actual conversion, namely the construction of a conversion scenario and the identification and testing of all the requirements. Therefore the process is explained by going through all the identified processes in figure 1, while addressing the common activities that are necessary for any of the identified conversion strategies briefly.
Figure 1 gives an overview of the parallel adoption process. The left side depicts the flow of activities that contribute to the process. Activities that run simultaneously are preceded by a thick black line. When the parallel running of activities is over, the activities are joined again in a similar black line. When there is no arrow from an activity to another, this indicates that they are aggregates of a bigger activity above. The activities are divided in four main phases:
- Define implementation strategy, that deals with the kind of implementation strategy should be executed.
- Pre-implementation, which has to do with constructing a planning of all aspects and requirements involved in the implementation.
- Prepare organization The organization should be prepared properly according to the previous phase.
- Conversion deals with the actual conversion process and closing the conversion process; proceeding with the new system.
The main phases are subdivided in other activities that will be described briefly in tables 1-1 to 1-4.
The right side of the model describes the data involved in the processes. Some of these concepts, depicted as a pair of overlapping open rectangles, can be subdivided in more than one concept. A pair of overlapping closed rectangles indicate a closed concept which means that it can be subdivided in more concepts, but it is not of further interest for the parallel adoption process. The diamond shapes figure indicates that the concept linked to it, serves as an aggregate concept and that this concepts consists of the other concepts. Finally the open arrow represents a super class-subclass relation. The concept linked with the arrow is the super class of the concepts that are linked to it. This syntax in figure 1 is according to Unified Modeling Language (UML) standards. The concepts in figure 1 are defined in table 2. More context for these sub activities in the process will be given underneath the tables.
Figure 1. Meta-process-data diagram of parallel adoption
Activity | Description |
---|---|
Define implementation strategy | The implementation strategy is determined in this early stage. (Brown, Vessey, 1999) |
Create master implementation script | The first initial requirements analysis is made, consisting of the requirements below. (Venture, 2004) |
Construct Time planning | A first time-planning of the implementation process is being constructed. (Rooijmans, 2003) |
Define Organizational requirements | The organizational requirements are defined here (Rooijmans, 2003). |
Define IT requirements | IT requirements are determined (Rooijmans, 2003) |
Activity | Description |
---|---|
Install requirements | In order to prepare the organization, the defined requirements are installed. The organization is being prepared and the IT installed on test-machines. (Rooijmans, 2003, Eason, 1988, Microsoft, 2004) |
Test requirements | The requirements are tested to see if the organization is ready for the implementation (Rooijmans, 2003) |
Redefine master implementation script | The master implementation script is refined with the new information gathered in the process with the activities below. (Rooijmans, 2003) |
Define criteria indicators | In order to test the new system, criteria indicators are being created. (Rooijmans, 2003, Microsoft, 2004) |
Formulate workaround/rollback plan | Also, a workaround plan with a rollback scenario is made. With these plans, the organization can respectively attempt to correct the mistakes that are made and fall back if the implementation in a certain stage of the process fails. (Microsoft, 2004, Rooijmans, 2003) |
Perform (segmental) Test conversion | In very complex organizations it can be beneficial to perform a test conversion, before going “live”. (Microsoft, 2004, Rooijmans, 2003) |
Activity | Description |
---|---|
Make catch ups | The conversion process is started, a number of activities run parallel. During this stage, catch ups are being made using the old system. The old system is leading, but the new one runs parallel. All changes in the system, have to be put in the new system. (Microsoft, 2004, Rooijmans, 2003) |
Control system | The system is being controlled at all times by the control system. With the defined indicators and system run characteristics, errors and mistakes are tracked down. (Microsoft, 2004, Rooijmans, 2003) |
Run leading old system | The old system is leading; processing the actual data. |
Run new system | The new system is running parallel with the old system and is closely monitored. (Microsoft, 2004, Rooijmans, 2003) |
Translate catch ups in new system | If the criteria are met, the catch ups are translated and transferred in the new system and the conversion process comes in its next stage. (Microsoft, 2004, Rooijmans, 2003) |
Execute workaround / rollback strategy | If the criteria are not met, the workaround strategy or rollback strategy is performed, depending on the nature of the errors. (Microsoft, 2004, Rooijmans, 2003) |
Make catch ups | Catch ups are made for safety purposes, even when the new system is leading. (Microsoft, 2004, Rooijmans, 2003) |
Run old system | The old system runs as a backup, for safety purposes |
Run leading new system(1) | The new system is leading and in full operation. All the transactions and changes in the system are being handled here. (Microsoft, 2004, Rooijmans, 2003) |
Activity | Description |
---|---|
Run leading new system(2) | All catch ups and controls are closed down. The new system is the only system in operation. (Microsoft, 2004, Rooijmans, 2003) |
Disable old system | The old system is not necessary anymore and is disabled. (Microsoft, 2004, Rooijmans, 2003) |
The concepts from figure 1 are defined in table 2-1 below.
Concept | Definition |
---|---|
Implementation strategy | The strategy that will be chosen to implement the new system. The options are big bang, phased, parallel adoption, pilot conversion or a combination of those four. (Turban, 2002, Rooijmans, 2003) |
Implementation script | Raw version of the actual conversion scenario, consisting of organizational requirements, IT requirements and an initial time planning. (Venture, 2004, Eason, 1988) |
Organizational requirements | Requirements from within the organization that should be present for a successful implementation. They deal with optimizing (changing) the organization for the new system. Issues involved can be: Human resources management, changing organograms and new business structures. (Rooijmans, 2003) |
IT requirements | The information Technology requirements are the software and hardware requirements, platform choices, taking into account budget and existing systems. (Rooijmans, 2003) |
Time planning | A planning in which activities are assigned a time-period wherein they should be completed, providing an overall picture of the implementation project with regard to available time. (Eason, 1988) |
Requirements | |
Conformity | Conformity is all about meeting requirements.(ISO 9000) |
Conversion scenario | The redefined implementation script, taking into account the conformity to the requirements. Furthermore the conversion scenario consists of a workaround and rollback plan. The conversion scenario is the blueprint of the implementation project. (Rooijmans, 2003) |
Workaround strategy | A backup plan; strategy taken on, in the conversion scenario to prevent errors in the conversion process and attempt to work around them, so that the implementation can still be successful. (Rooijmans, 2003) |
Criteria indicators | Quantifiable and measurable criteria with regard to the requirements, to determine if the implementation process was successful. (Rooijmans, 2003) |
Rollback plan | Plan that facilitates in reversing the direction of the replication in order to go back to the old system without loss in data or information. (Microsoft, 2004) |
Test conversion | Segmental test conversion, before the actual conversion takes place with as goal to be better prepared against uncertainties or problems in the actual conversion process. (Microsoft, 2004) |
Old system | The old system: when leading = true; the old system handles the system transactions live: The principal functioning entities comprising the product, e.g. hardware, software. Also an organized and disciplined approach to accomplish a task, e.g., a failure reporting system (ISO 9000) |
New system | The new system (goal): The new system, when leading = true; the new system handles the system transactions live. The principal functioning entities comprising the product, e.g. hardware, software. Also an organized and disciplined approach to accomplish a task, e.g., a failure reporting system (ISO 9000) |
Control | The overall control system comprising performance indicators as well as a reliability assessment and catch ups. The control system is very broad and is the central command system of converting the old system and managing the new one during the parallel adoption process. (Rooijmans, 2003, Microsoft, 2004) |
Performance | Quantifiable assessment of performance of the old and new system serves as input for the control system. (Rooijmans, 2003) |
Reliability assessment | A quantitative assessment of the reliability of a product, system or portion thereof. Such assessments usually employ mathematical modeling, directly applicable results of tests on the product, failure data, estimated reliability figures and non-statistical engineering estimates. (ISO 9000) |
Catch ups | Catch ups consist of automatically or non-automatically created back-ups of the system using the old system, to be translated in the new system. (Rooijmans, 2003) |
Automatic catch ups | Automatically created catch ups (Rooijmans, 2003) |
Catch up by hand | Catch ups created by manual input (Rooijmans, 2003) |
Determining the parallel implementation strategy[edit]
The parallel adoption is preceded with determining the implementation strategy, which is not unique for parallel adoption, but can be seen as part of the change management process that an organization enters. (Lee, 2004). Some factors involved in determining an implementation strategy regarding adoption methods is described more thoroughly in Adoption (software implementation).
Risk versus costs[edit]
The reason for an organization to choose for parallel adoption in favour of a pilot conversion, big bang or phased adoption is often a trade-off between costs and risk (Andersson, Hanson, 2003). Parallel adoption the most expensive adoption method (Chng, Vathanopas, 2002, Microsoft, 2004, Anderson et al., 2003), because it demands from the organization that two systems run parallel for a certain period. Running two systems simultaneously means that an investment in Human Resources has to be made. Besides a good preparation of the (extra) personnel, that has to go through a stressful period of parallel running where procedures cross each other. (Rooijmans, 2003, Eason, 1988) Efforts should be placed on in: Information Technology and Organizational Change. London: Taylor & Francis
Parallel Definition In English
Parallel Conversion Definition
External links[edit]
- Replatforming Line of business Applications from UNIX to Windows. (2004), version 1.0 Microsoft, Retrieved March 5, 2006 [1]
- Implementing a portfolio accounting system: Lessons from the trenches (2004), Venture Financial Systems Group Ltd, Retrieved March 6, 2006 [2]
Parallel Lines Definition
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