1. Requirements

4.1.1 The project shall develop a Software Configuration Management Plan that describes the functions, responsibilities, and authority for the implementation of software configuration management for the project.

1.1 Notes

The Software Configuration Management Plan may be a part of the project configuration management plan. The content is defined by the requirement in Chapter 5 [of NPR 7150.2, NASA Software Engineering Requirements, Section 5.1.2].

1.2 Applicability Across Classes

Class G is labeled with "P (Center)." This means that an approved Center-defined process which meets a non-empty subset of the full requirement can be used to achieve this requirement.

2. Rationale

"Software configuration management is practiced during all phases of the software life cycle, from initiation of development through software maintenance, and is responsible for ensuring that any changes during the development and maintenance processes are made in a controlled and complete manner... Configuration management contributes to software safety by ensuring that documentation and source code are updated only through a formal process." (NASA-STD-8719.13B, NASA Software Safety Standard) ²⁷¹
NASA-GB-8719.13, NASA Software Safety Guidebook, ²⁷⁶ describes the software configuration management (SCM) plan in this manner: "All software products, which includes far more than just code, must be configuration managed. Old files in a software build are a notorious problem, as are lost updates and other problems with changed files. The plan specifies what will be under configuration management (CM), what CM system will be used, and the process for moving an item into or out of the CM system."

Given that CM occurs throughout the project life cycle and is critical to controlling and tracking all elements of the project, having a plan in place ensures that the team is informed of and performs all necessary and required configuration management tasks. Development of the SCM plan provides the opportunity for stakeholders to give input and assist with the documentation and tailoring of the planned configuration management activities for the project. 

The SCM plan has both internal and external uses. Internally, it is used within the project to guide, monitor, and measure the overall CM process. It describes both the CM activities planned for future acquisition phases and the schedule for implementing those activities.  Externally, the SCM plan is used to communicate the CM process to the contractors involved in the program. It establishes consistent CM processes and working relationships. (NASA Systems Engineering Handbook ²⁷³)

3. Guidance

The SCM plan describes the software configuration management for the project, including functions, responsibilities, and implementation authority. This plan may be part of the software development plan (SDP)/software management plan (SMP) or it may be a standalone document. If the plan is a standalone document, part of its content needs to describe the SCM plan's relationship to other project plans, especially if configuration management activities are referenced or described in those plans.

The SCM plan primarily provides a formal method for managing change, but other activities are key to the overall process and are also appropriate to describe in the plan. See SWE-103 in this Handbook for guidance on required contents, but consider the following topics as well when developing the SCM plan:

• CM of deliverable and non-deliverable software development products including the following:
  • Documentation (e.g., specifications, design documents, traceability matrices, presentations, project plans).
  • Source code.
  • Object code.
  • Executables.
  • Data.
  • Development and test tools (operating systems, compilers, etc.).
  • Development and test environments (both hardware and software).
  • Testing software (e.g., test cases/scenarios, scripts (manual and automated), reports).
  • Flow charts, UML (Universal Modeling Language) or OOD (Object Oriented Design) products, input to automatic code generators.
  • Interface control documents, message formats, data formats
  • COTS (Commercial Off the Shelf) software.
  • Build procedures.
  • Defect lists, change requests, problem reports/corrective actions.
  • Metrics.
• CM of software assurance records.
• CM of safety-critical software requirements and software elements.
• CM of simulators, models, test suites, etc.
• Management of releases.
• CM of routine software configuration changes, such as mission-specific database changes.
• Assessment of changes for their impact on system safety.
• Metrics to be collected from the CM system, such as lines of code, complexity, estimated and actual time for various activities (development, testing, bug fixes, etc.), number of defects.
• Determinations that can be made from configuration metrics, such as defects per lines of code for a team, goodness of effort estimations, need for more time in unit testing, estimates for future updates/maintenance activities, etc.
• Processes for "handling classified information and sensitive but unclassified (SBU) information, including export controlled and proprietary information, as applicable." (NASA Configuration Management (CM) Standard ²⁷⁵)

When writing the SCM plan, consider the following tailoring suggestions from IEEE STD 828-2005  ²¹⁶:

• Reflect the current project environment by using terms familiar to the planned users and maintaining consistency with project development processes.
• When tailoring leads to the addition of SCM requirements for a particular project (beyond the minimum specified in a template, standard, etc.), conduct a cost-benefit analysis and obtain agreement from stakeholders.
• When tailoring leads to the removal of SCM requirements for a particular project (from the minimum set specified in a template, standard, etc.), include the rationale for the removal (project has limited scope, unusual environment, etc.) and obtain agreement from stakeholders.

The SCM plan may also be tailored by software classification. Goddard Space Flight Center (GSFC)'s Requirements for Minimum Contents of Software Documents ⁰⁹⁰ provides one suggestion for tailoring an SCM plan based on the required contents and the classification of the software being developed.

Development of the SCM plan, typically by engineering, begins during project formulation. Inputs to developing the project-level plan include the program CM plan, the IEEE Standard for Software Configuration Management Plans (IEEE STD 828-2005), and any Agency or Center-specific templates and guidance material.

Once the SCM plan is created, it is peer reviewed (SWE-137), coordinated with the project customer and other stakeholders, and reviewed at project milestone reviews, such as the System Requirements Review (SRR), Software Requirements Review (SwRR), Mission Definition Review (MDR), etc. (see Topic 7.08 - Maturity of Life Cycle Products at Milestone Reviews). The SCM plan needs to be reviewed by software assurance to ensure compliance with applicable standards, procedures, and to ensure the plan is being properly implemented.

Additional guidance related to CM and topics that have to be addressed in the SCM plan may be found in the following related requirements in this Handbook:

4. Small Projects

CM activities are based on risk, so projects designated small by size of the team or budget need to ensure that their SCM (Software Configuration Management) plans consider all the required content noted in SWE-103, but only include those processes and the associated structure commensurate with project risk. This might mean planning to use simpler tools or fewer personnel (filling multiple roles) to carry out the SCM processes.  It could also mean planning to use a single tool for multiple purposes to reduce tool management and overhead. Note that waivers may be necessary if any required content is left out of the SCM plan.

Small projects may not require the formality of a separate SCM plan; instead SCM planning may be documented as a section of the project's Software Management Plan. Alternatively, one master SCM plan may document CM for multiple small projects.

5. Resources

5.1 Tools

Tools to aid in compliance with this SWE, if any, may be found in the Tools Library in the NASA Engineering Network (NEN).

NASA users find this in the Tools Library in the Software Processes Across NASA (SPAN) site of the Software Engineering Community in NEN.

The list is informational only and does not represent an “approved tool list”, nor does it represent an endorsement of any particular tool. The purpose is to provide examples of tools being used across the Agency and to help projects and centers decide what tools to consider.

6. Lessons Learned

The NASA Lessons Learned database contains the following lessons learned related to the importance of configuration management:

• Software Design for Maintainability (Software maintainability). Lesson Number 0838: "Configuration management of software is probably the single most important management and maintainability concept utilized in software development. Utilization of coding standards, documentation standards, release standards, common languages and other methods will provide for good configuration management. A plan should be developed very early in the development cycle for managing the configuration of the software under development, and that plan should be followed rigorously. If configuration management breaks down, the code under development is doomed to be extremely troublesome when released for operations." ⁵²⁶
• Computer Software/Configuration Control/Verification and Validation (V&V) (Auto-generated code). Lesson Number 1023: "The use of the ... autocode generator for ISS software can lead to serious problems if the generated code and ... [tool] itself are not subjected to effective configuration control or the products are not subjected to unit-level V&V. These problems can be exacerbated if the code generated ... is modified by hand." ⁵³³
• Take CM Measures to Control the Renaming and Reuse of Old Command Files (2002) (File naming). Lesson Number 1481: "The ... Team renamed a ... file ... prepared for a previous mission for use on a current mission without changing the file creation time recorded in the file header. This error caused the new file to be repeatedly recognized as an 'old' file, and required operations personnel for several months to manually specify the correct file. Implement CM (Configuration Management) measures to assure adequate oversight when renaming old command sequence resources for reuse." ⁵⁵⁶