During execution of the project, we may come across one or more of the following possibilities:-

• Some or all activities are progressing according to schedule
• Some or all activities are ahead of schedule.
• Some all activities are behind schedule.

Based on the progress of the activities, the revised durations of unfinished activities due to delays, the network diagram has to be redrawn. This process is known as updating of network

Data required for updating are:

• Original network
• Original network calculation chart
• Stage at which updating is being done i.e. a point in time of updating
• Execution position of the project at that stage.
• New information and knowledge which will affect the duration time of the activities to be performed.

The following points must be kept in mind while deciding the time of updating:-

• For shorter duration project, the updating must be done frequently by taking into account the latest position of the execution of the project.
• For large duration of project, the process of updating must be increased as the project progresses toward completion.
• Whenever there is major change in the duration of any activity updating is to be done.
• Updating is essential if there is change in the duration of and activity falling on the critical path.

Steps in the process of updating are as follows:

• To describe the point at which updating is to be done according to the original plan.
• To record work progress what has happened actually till the updating point.
• To summarize the knowledge obtained in the tabular form.
• To place the information contained in the updating table on to the original network.
• To perform calculations of EST and LST and mark these on the network known as updated network.