Legacy system

It is possible to implement the Scheduler without a Session class and without unique and distinct objects for each session such an approach would be quite common when you re assembling existing implementation components or legacy systems, such as a calendar (with events) and an employee database (with employees). When designing, some people like to distinguish those types they have decided to implement—design types— from those that are used simply to help write a specification—spec types. Design types can be drawn with a heavier border. 

We should not assume that objects are intrinsic to component-based development in fact, one of the advantages of components is that they can encapsulate legacy systems regardless of how the systems are implemented inside. The idea of components goes back almost as far as the idea of software, but a number of things have changed significantly over the years. 

Components need not be little things they can be entire applications or legacy systems. The nature of the connectors between these components differs. The components shown in Figure 10.9 are the support systems for some of the departments in a large manufacturing company. 

Legacy adapter This thin layer shields business objects from idiosyncrasies of the legacy system and its representations. 

Known platform or architectural constraints Machines, operating systems, distribution, middleware, legacy systems, and interoperability requirements, all captured by a package structure and collaborations... 

Pattern 16.6, Separate Middleware from Business Components, offers one strategy for handling legacy systems as well as for insulating the project from certain technology changes. 

To define the scope and boundary of a system and its relation and interactions with its immediate environment to build the requirements spec for a system or subsystem to be installed or to review the context of a legacy system. 

The point of this pattern is to separate business components from others. Wrap legacy systems behind a layer of objects representing the business concepts. Transition from custom infrastructure solutions to standardized middleware, enabling integration and extension of disparate systems in a way that is shielded from technology changes. 

The objective is to build new business components that can integrate with legacy systems and across disparate systems while shielding the system from technology changes. 

The legacy system might be only a file server or a relational database. Or it might be a higher-level component, such as a spreadsheet with an API, or a complete application such... 

Client interface Business component Legacy systems... 

The first benefit is platform independence. The business objects can be written independently of the legacy systems and can be ported. Using middleware, you can integrate new application components with existing application code and purchase components to build seamless business systems. 

Components in Catalysis need not be built using object technology. The concept of a type model and operation spec can be applied equally to a Java, C++, COBOL, or assembler implementations—and therefore to legacy systems—thanks to refinement. 

Network (including communication links). Legacy systems hardware and software have very limited security capabilities, and the vulnerabilities of contemporary systems (based on modern information technology) are publicized. Wireless and shared links are susceptible to eavesdropping and data manipulation. 

For those records that remain subject to Part 11, enforcement discretion will be exercised with regard to Part 11 requirements for validation, audit trails, record retention, and record copying in the manner described in the guidance and with regard to all Part 11 requirements for systems that were operational before the effective date of Part 11 (also known as legacy systems). 

Legacy Systems The FDA intends to exercise enforcement discretion with respect to all Part 11 requirements for systems that otherwise were operational prior to August 20,1997. Thus they do not intend to take enforcement action to enforce compliance with any Part 11 requirements if all of the following criteria are met for a specific system ... 

Existing system applications will need to be evaluated and applicable GMP issues and risks identified. Whether it be legacy systems, systems to be revalidated, or systems yet to be validated, the critical parameters, data, and functions that direcdy impact GMP should be clearly identified and formally documented. Each system should be assessed under a formal procedure to determine compliance with the regulations for electronic records and electronic signatures. Any resulting action plan should include system prioritization and implementation timings. 

As defined in CPG 7153.17, legacy systems are computer systems not in compliance with Part 11. The first fundamental principle of Part 11 is that it requires organizations to store regulated electronic data in its electronic form. The second fundamental principle is the high level of security required to protect regulated electronic records. 

If evaluation results do not meet the current regulatory requirements, then the retrospective evaluation would not in itself support the trustworthiness of the electronic records. This is an area of concern for electronic records recorded using legacy systems after August 1997. 

Once a legacy system has achieved a satisfactory, documented Part 11 compliant state, any subsequent changes can be prospectively validated. 

The FDA defines legacy systems as those systems in place before August 20, 1997.1... 

This clause applies to legacy systems and the electronic records stored by these systems. The no grandfathering clause indicates that Part 11 provisions relating to record creation do not cover electronic records that are created before the effective date of the rule. These records would not need to be retrospectively altered. 

Legacy systems Production computer systems that are operating on older computer hardware or are based on older software applications. In some cases, the vendor may no longer support the hardware or software. 

In other cases, the electronic records will not be converted for use by the new system. In this case, the obsolete system could be maintained as a legacy system, and utilized to access the electronic records. This approach can be expensive and is one that might still require the transfer of the legacy data to the new system or format at a later date, when maintenance becomes impractical. 

On September 3, 2003 the FDA released the final guidance on the Scope and Application of 21 CFR Part 11. Comments from industry played a large role in the changes that the FDA made between the draft version and the new final version. Significant clarification was also established on the definition of legacy systems and on enforcement discretion . 

Running the legacy system, manual or automated, in parallel with the new system for the period of the process PQ is often not a practical option. In such circumstances processes, such as additional data checks and report verification, should be temporarily operated in parallel with the computer system until the completion of PQ. 

Simple There is an obvious legacy field equivalent, or lack of equivalent, to the new system field. Complex There is information in the legacy environment but, before it is suitable for entry into the new system, the field length or format needs to be changed. Perhaps the field needs to be transformed, several fields need to be eombined, a field in the legacy system needs to be split to feed several fields in the new system, or there may be a combination of all or some of these. 

Suppliers usually make sure their products are backward compatible so that legacy systems can be seamlessly replaced by new systems. Suppliers typically develop their upgrades for use on the same hardware platform. Full compatibility, however, is more than this. The new product must... 

With every software upgrade, either of the application or an operating system, the validity of previously recorded data hies should also be checked. This can be achieved by comparing the data derived from a legacy system with the data derived from the system upgrade. 

Discontinuity in use of legacy systems (may also be advantage to new owner)... 

The new owner shonld ensure operation and maintenance procedures are clearly marked as approved and operated by them when they take over responsibihty for supporting the legacy systems. 

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