1. Software Configuration Management

2. Software Configuration Management (SCM)
The process of identifying, organizing, and controlling changes to the software during development and maintenance.
SCM is a support activity that makes technical
and managerial activities more effective
SCM operates throughout the SW life-cycle

3. Causes of Change Evolutionary changes Revolutionary changes
the system evolves as it passes through various stages in the development cycle
Revolutionary changes
such change is caused by the system being unable to satisfy the user’s requirements or the customers or producers expectations

4. Why Products change ? Requirements change during and after development
Errors are found and need correction
Variants are needed

5. Problems of Change Which component ? Which version ?
Double (or multiple) maintenance
Updates to shared data
Simultaneous update

6. SCM Functions Identification of software items and products
Definition of Baselines
Access controls
Progressing defect reports
Progressing change requests
Recording item status
Controlling releases (versions and variants)
Reporting

7. SCM Tasks Configuration identification Configuration control
Status accounting
Configuration audit

8. Some Definitions ... Development item not yet approved, can
item be informally changed
Configuration an approved and accepted
item (CI) deliverable, changes done
through formal change
control procedures

9. Typical SW Configuration Items (CIs)
Management plans
Specifications (requirements, design)
User documentation
Test design, case and procedure specifications
Test data and test generation procedures
Data dictionaries and databases
Source code, executable code
Libraries
Maintenance documentation
Support software

10. Milestones and Baselines
A milestone is the end of a stage or phase of a project at which one or more deliverables are actually delivered.
Baselines
A baseline is that collection of items which when complete indicates that a milestone in the development process has been reached.

11. Typical Baselines Phase Baseline Feasibility study
Requirements defn. Functional baseline
SRS, Interface spec. Allocated baseline
Detailed design Design baseline
Source and Object code
User manuals
Test documents Product baseline
Installation Operational baseline

12. Baselines Baselines serve as the basis for further development
Baselines can be changed only through formal change control procedures
Only items that have been approved and obtained through a formal technical review are accepted into the baseline.

13. Configuration Identification
Identify what the different baselines will consist of
Set labelling and identification conventions for the CIs

14. Basic CI information Item identity Baseline to which it belongs
Relationships to other items
Version
Variant

15. SCM Terminology Version
A SW CI having a defined set of functional capabilities.
Revisions
changes to a version to correct only errors in design logic but does not affect documented functional capabilities since none of the requirements have changed.
Variants
a variation of a version developed to run on different types of HW, or to provide slightly different facilities for different users.

16. Examples successive versions 1.1 1.2 1.3 1.4
branching versions (variants)
1.1
1.2
1.3
1.4

17. Merging
Two diverging versions may be merged to create a single new version combining both set of change requests.
Merge operations are typically done interactively with tool assistance

18. SCM Terminology Promotion of a CI
A CI may be promoted from one developmental baseline to another to signify a change in a CI’s internal development state.
Release
A Release is used to designate certain promotions of CI’s that are distributed outside the development organization.

19. Configuration Control
Enforces a rigorous change control mechanism
Requires formal procedures to
request changes
carry out impact analysis
approve changes
carry out changes

20. Change Management Methodology
Submission of Change Request (CR)
Technical and business evaluation and impact analysis
Approval by Change Control Board
Engineering Change Order (ECO) is generated stating
changes to be made
criteria for reviewing the changed CI
CI’s checked out
Changes made and reviewed
CI’s checked in

21. Change Control Board
A group consisting of representatives of user, customer, producer.
Responsibilities:
to approve, monitor and control baselines
to approve, monitor, and control changes
to authorise changes
CCB concerns in change approval
technically ok solution, cost, schedule, configuration of the whole system, user satisfaction

22. Software Libraries SW libraries provide the means for implementing SCM
The number and kind of libraries will vary from project to project . It depends on the levels of control needed.

23. Three Kinds of Software Libraries
Dynamic library (programmer’s library)
programmer’s workspace
Controlled library (master library)
used for managing the current baseline(s) and for controlling changes made to them
Static library (software repository)
used to archive various baselines released for general use

24. Techniques for storing Versions
Full files
Forward Delta files
Reverse Delta files
The set of differences between two versions is called a delta.

25. Forward Delta Files + User CM System foward delta files Vn version Vn
first
version
changes
Vn+1
version
Vn+1
version Vn
version

26. Reverse Delta Files + User CM System reverse delta files Vn+1 Vn+1
version
Vn+1
new recent
version +
changes
recent version Vn
version Vn
version

27. Status Accounting
provides a mechanism for administrative tracking and reporting of all SW items identified and controlled.
Examples of Status reports:
the status of proposed changes
the status of approved changes
the baselines and the approved changes associated with each baseline
the date when each revision of each CI was recorded
deficiencies identified by configuration audit

28. Configuration Audit
A configuration audit establishes that product integrity has been maintained and that changes have taken place in an orderly and controlled manner.
Audit of the SW product
Audit of SCM activities

29. Physical Configuration Audit
consists of determining that all items identified as being part of the configuration are present in the Product baseline
it must also establish that the correct version and revision of each part are included in the product baseline and that they correspond to information contained in the baseline’s configuration status report.

30. Functional Configuration Audit
it verifies that each CI in the product has been tested to determine that it satisfies the functions defined in the specifications or contract(s) for which it was developed.

31. Organising for SCM Roles: Configuration manager Change Control Board
includes representatives of
- user
- customer
- developer

32. SCM Plan
The SCM Plan is prepared in Project Initiation phase. It documents
- what SCM activities are to be done
- how they are to be done
- who is responsible for doing specific
activities
- when they are to happen
- what resources are required

33. SCM Tools
Common features of popular PC-based tools (PVCS, MS Visual SourceSafe):
Support for controlling all types of files (source code as well as binary)
Managing changes as deltas
Supporting branching and merging
Identifying and re-creating releases
Providing a project view

34. Intersolv PVCS Version Manager 5.2
One of the oldest PC-based version control products
Large installed base
A fairly rich feature set
Interfaces with other third party tools
Gateways to mainframe-based library management systems
Comprehensive security

35. Microsoft Visual SourceSafe 4.0
Project support
File sharing
Intuitive GUI interface
Good repository architecture
Powerful security features
Tight integration with Visual Basic and Visual C++ development tools

36. SCM Tools for Unix SCCS (Source Code Control System)
manages changes to text files
uses a single file (s-file) to store first version and successive forward deltas
RCS (Revision Control System)
uses reverse deltas to store versions

37. SW Configuration Management Plan
-- IEEE Standard for SCM Plan
1. Introduction
2. SCM Management
2.1 Organization
2.2 SCM Responsibilities
2.3 Applicable policies, directives and procedures

38. SW Configuration Management Plan
-- IEEE Standard for SCM Plan
3. SCM Activities
3.1 Configuration identification
3.1.1 Identifying configuration items
3.1.2 Naming configuration items
3.1.3 Acquiring configuration items
3.2 Configuration control
3.2.1 Requesting changes
3.2.2 Evaluating changes
3.2.3 Approving or disapproving changes
3.2.4 Implementing changes

39. SW Configuration Management Plan
-- IEEE Standard for SCM Plan
(3. SCM Activities)
3.3 Configuration Status Accounting
3.4 Configuration Audits and Reviews
3.5 Interface control
3.6 Subcontractor/Vendor control
4. SCM Schedules
5. SCM Resources
6. SCM Plan maintenance