1. Configuration Management
Seminar in Software Design /6
Aviva Dayan
Arik Gendelman
Pablo Galiana

2. What is Configuration Management?
The control of changes made throughout the system lifecycle.
Allows changes to be evaluated before they are approved.
Considers interrelationships among system components.
Configuration Management

3. Software Configuration Management
A software engineering discipline
Comprised of tools and techniques
used to manage change to software assets.
A set of activities to control change by:
identifying the products & establishing relationships
defining mechanisms for management, control, auditing and reporting on changes made.
In short: “A methodology to control and manage a software development project.”
Configuration Management

4. Configuration Management
Why do we need SCM?
To manage:
Many people working on the same code.
Projects delivered in several releases (builds).
Rapid evolution of software and hardware.
Project surveillance:
i.e. project’s status, bugs, features, etc.
Concurrent support and development.
Stress time requirements of projects.
Configuration Management

5. Configuration Management
Goals of SCM
Configuration Control
Controlling product release and its updates.
Status Accounting
Recording and reporting components’ status.
Review
Ensuring completeness and consistency of all parts.
Build Management
Managing the build process and its tools.
Configuration Management

6. Configuration Management
Goals of SCM – cont.
Process Management
Ensuring adherence to the development process.
Environment Management
Managing the components that host our system.
Teamwork
Facilitate team interactions
Configuration Management

7. SCM – How it is accomplished?
All these goals are accomplished through
Version control
Management of multiple revisions of the same unit of information.
Configuration Management

8. Configuration Management
Version control
Commonly used in engineering and software development.
Changes identified by incrementing an associated number or letter code - “revision number”, or “revision level”.
Revision numbers (levels) are associated historically with the person making the change.
Configuration Management

9. Configuration Management
Vocabulary
Repository
A server where the files are stored.
Check-Out
copies a working copy from the repository
(the opposite of an import).
Change
A specific modification to a document under version control.
The granularity of the modification considered a change varies between version control systems.
Configuration Management

10. Configuration Management
Vocabulary – cont.
Change List
The set of changes made in a single commit.
A sequential view of the source code.
Commit or Check-in
Copy the changes on the local files to the directory.
(the VC software takes care of changes since the last synchronization).
Update
copies the changes that were made to the repository into your working directory.
(opposite of a commit).
Configuration Management

11. Configuration Management
Vocabulary – cont.
Merge / Integration
brings together (merges) concurrent changes into a unified revision.
Revision or version
one version in a chain of changes.
Conflict
Occurs when two changes are made by different parties to the same document or place within a document.
Resolve
The act of user intervention to address a conflict between different changes to the same document.
Configuration Management

12. Configuration Management
Example
CM Clients
CM Server
Trunk
Version A Branch
Machine A
Check Out A
Version A.1 Branch
Check In C
Machine B
Version B Branch
Check Out B
Merge D
Check In E
Configuration Management

13. Configuration Management
History
CM systems save the files’ history.
Old versions can be viewed, compared, and downloaded.
New versions can be (irreversibly) replaced with old versions and ‘wiped off the map’.
Configuration Management

14. Configuration Management
Central repositories
Files are saved in a central file server.
Developers can view the files in the repository, through the use of filters.
Configuration Management

15. Configuration Management
Labels
Several files can be labeled together.
Allows :
Access to the label as a whole set of files.
Changes to the labeled files as a unit.
Useful for marking product releases.
Configuration Management

16. Configuration Management
Check-in
Copies a file into the database.
The version you see is (usually) the latest version that was checked in.
The old version is kept and can be accessed later.
Configuration Management

17. Configuration Management
Check out
Copies the database file to your personal folder, and raises a flag on the database copy.
Need to check out before checking in.
Configuration Management

18. Undo check out (uncheck-out)
The “undo checkout” command does just that – the file returns to the status it had before it was checked out.
This can be done even if changes have been made to the local copy – of course, these do not go into the database!
Configuration Management

19. Configuration Management
Versioning Models
Lock-Modify-Unlock Solution:
Only one person can change a file at a time.
Example: VSS.
Copy-Modify-Merge Solution:
Users modify private copies only - in parallel
Private copies are merged together into a new, final version.
Example: CVS, Subversion.
Configuration Management

20. Configuration Management
Problems With Locking
Administrative problems:
A user can lock a file and forget about it.
Time is wasted while others wait to edit the file.
Unnecessary serialization:
Different parts of a file don’t necessarily overlap.
E.g.: Alice works on the beginning of a file, Bob wants to edit the end of the same file.
Configuration Management

21. Problems With Locking – cont.
False sense of security:
Let’s say Alice locks and edits file A, while Bob simultaneously locks and edits file B.
Let’s say A and B depend on one another, and the changes made to each are semantically incompatible.
Suddenly, A and B don't work together anymore.
Configuration Management

22. The Copy-Modify-Merge Solution
Aviva and Arik both check out file A.
Here, checkout has no locking effect – it’s just a local copy.
Repository A
Read
Read A A
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23. The Copy-Modify-Merge Solution
Both edit their local files.
Repository A
Aviva
Arik
Configuration Management

24. The Copy-Modify-Merge Solution
Aviva checks in her file to the repository first.
Repository
Aviva
Write
Aviva
Arik
Configuration Management

25. The Copy-Modify-Merge Solution
Now, Arik tries to check-in his file.
He gets an “up-to-date check error”
Repository
Aviva
Aviva
Write
Arik
Configuration Management

26. The Copy-Modify-Merge Solution
Arik updates his local copy to contain the changes made by Aviva. Changes are added to the local file.
During this merge, conflicts may occur.
Repository
Aviva
Aviva
Read A’
(=Aviva+Arik)
Configuration Management

27. The Copy-Modify-Merge Solution
A new merged file is created on Arik’s machine.
Repository
Aviva
Aviva B
Configuration Management

28. The Copy-Modify-Merge Solution
Arik commits his file to the repository.
Repository B
Write B
Aviva
Configuration Management

29. The Copy-Modify-Merge Solution
Aviva updates her file from the repository.
Repository B
Read B B
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30. Configuration Management
Check-out etiquette
If two people have a file checked out, they have to merge their changes before check-in
Merging files can be messy!
This requires coordination and responsibility on the part of developers, not to make unnecessary check-outs, and not to hold check-outs for too long.
Configuration Management

31. Configuration Management
File Comparison
Users can graphically compare two versions of files, in or out of the database.
Tools: BeyondCompare, Windiff, AraxisMerge…
This helps with manual merges
Also helps people decide which version to access
Configuration Management

32. Configuration Management
SourceSafe
Central repository of read-only files.
Everybody sees the same version.
Only one user can check in at once.
No branching.
Limited merge capabilities.
Synchronized with Visual Studio
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33. Advantages of SourceSafe
Synchronized with Visual Studio.
Relatively inexpensive.
Relatively simple to administrate.
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34. Disadvantages of SourceSafe
Does not support branching
Requires verbal coordination.
Poses a problem for large projects.
Complicates development of features
Not compatible with other OS’s.
Configuration Management

35. Configuration Management
Get Latest Version (?)
Getting the latest version copies (rather than links) the file from the database to your personal directory - And so:
Getting latest version overwrites files in personal folders.
Rename local files beforehand if you want to keep them.
Database updates do not update local copies.
Changes to database necessitate manual merges.
Configuration Management

36. Preserving Database Integrity (or: watch SourceSafe limp…)
Before a SourceSafe check-in:
Verify thoroughly that the modified file works with other files
Otherwise there could be big trouble…
Other systems allow for new branches
Files can be updated there.
Branch is merged with main trunk only after integrity checks.
Advantage: source control throughout the checking process!
Configuration Management

37. Configuration Management
Demo- SourceSafe
Demo – SourceSafe
Configuration Management

38. Concurrent Versions System
CVS has UNIX origins.
Available also for Linux and Windows.
Stores only the differences between versions.
Configuration Management

39. Configuration Management
Clients
Command line.
GUI (i.e. WinCVS, tkCVS, etc)
NOTE: Most GUI/Plugins are wrappers around the basic CVS command line client.
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40. Configuration Management
Revisions
Each version of a file has a unique Revision number. Revision numbers look like ‘1.1’, ‘1.2’, ‘ ’ or even ‘ ’.
1.1
1.2
1.3
1.4
Main.c
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41. Configuration Management
Revision Numbering
By default:
revision 1.1 is the first revision of a file.
Successive revisions incremement the rightmost number.
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42. Configuration Management
Tags
Tags are used to give a symbolic name to a certain collection of file revisions.
Main.c
1.1
1.2
1.3
1.4
TAG_XXX
Main.h
1.1
1.2
Lala.c
1.1
1.2
1.3
Configuration Management

43. Configuration Management
Branching
Like ClearCase, CVS allows branches:
Allows changes to be isolated into a separate development line.
Branches are good for:
Fixing bugs in historical releases.
Developing features without disrupting primary development.
Configuration Management

44. Configuration Management
Trunks and Branches
The main branch is called the “main trunk”.
A branch can be merged back to the main trunk, or left as a branch.
Configuration Management

45. Branches and Revisions
Branch >
Branch >
1.1
1.2
1.3
1.4
Main Trunk
Main.h
Branch >
Configuration Management

46. Configuration Management
ClearCase - Overview
Rational ClearCase is a software tool for revision
control of source code and other software
development assets.
Basic concepts:
Items under ClearCase are generally referred to
as “elements”.
For example:
design models, source files, project files, DLLs, etc.
Configuration Management

47. Configuration Management
VOB
All elements stored in VOBs – Version Object Bases.
Depending on the size and complexity of your SW
development environment – ClearCase elements
may be distributed across more than one VOB.
For example:
elements used by the Documentation group can be stored in one VOB, while elements contributing to software builds can be stored in a different VOB.
Configuration Management

48. Configuration Management
VOB – Illustration
This diagram
illustrates a VOB
that contains the
file elements :
prog.c,
util.h,
msg.cat,
and lib.c
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49. Configuration Management
View
To access an element under ClearCase, you set up and work in a view,
A view shows a directory tree of specific versions of the element.
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50. Configuration Management
Two kinds of views:
Snapshot views
copy files from VOBs to your computer.
Dynamic views,
use the multiversion file system (MVFS) of ClearCase to provide immediate, transparent access to the data in VOBs.
Configuration Management

51. Configuration Specifications
A set of rules called a configuration specification determines which files are in a view.
These rules are written in a special and powerful script language.
Configuration Management

52. Configuration Management
Version Trees
Each time an element is revised and checked in, ClearCase creates a new version of the element in the VOB.
ClearCase organizes the different versions of an element in a VOB into a version tree.
Configuration Management

53. Version Trees and Branches - Illustration
This
diagram
illustrates a
version tree
and several
branches:
Configuration Management

54. Advantages of ClearCase
Can handle projects that:
a) Consists from a lot of developers.
b) Go on for a very long time.
Developed and marketed by IBM,
i.e. very smooth and natural integration with a lot of other IDE/CM/test/profiling… Tools.
Versatile – lots of possibilities and capabilities.
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55. Configuration Management
Advantages – cont.
Supported by multiple OS
Windows, Unix (Solaris, AIX, …), Linux.
Can be accessed from client on one OS to a server on another OS.
Enables real parallel development - work on multiple versions of the same source file concurrently.
Configuration Management

56. Configuration Management
Disadvantages
High price.
Too versatile
one can never learn all capabilities.
Complex support
must have very good - full time - administrator.
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57. Configuration Management
ClearCase View Snapshots
Windows Unix
Configuration Management

58. ClearCase Integrated in Visual Studio IDE.
Configuration Management

59. Checkout Operation Snapshot Windows Unix
Configuration Management

60. ClearCase Merge Utility Windows Unix
Configuration Management

61. Version Tree Snapshot Windows Unix
Configuration Management

62. General Info – Unix version
General information about a file in the repository – in the Unix GUI.
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63. Configuration Management

64. Configuration Management

65. Configuration Management
THE END
Configuration Management