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Slack and critical tasks

About Slack or „float”
Slack or „float” is the amount of time that a task can slip before it affects another task or the project's finish date. Use the „Early Start”, „Early Finish”, „Late Start”, „Late Finish”, „Start Slack”, and „Finish Slack” fields to analyze project schedule delays and find available slack in your schedule.

Find free slack in your schedule
  1. Choose „Task Sheet” (or any other task view with a table portion) > „Schedule Table” in the „Views” toolbar icon.
  2. Review the values in the „Free Slack” and „Total Slack” column.

Slack values may also indicate a schedule inconsistency. For example, a negative slack value occurs when one task has a „Finish-to-Start” dependency with a successor task, but the successor task has a „Must Start On” constraint that is earlier than the end of the first task.

About critical tasks
By default, iTaskX defines a task as critical if it has zero days of slack. However, you can change this definition and make a task critical if it has, for example, one or two days of slack. Making a task with slack critical can be helpful if you want to be alerted to tasks that are becoming critical when you still have some buffer.
Slack is determined by the early finish and late finish dates of the tasks in your schedule. An early finish date is the earliest date that the task could finish, based on its start date and scheduled duration. A late finish date is the latest date that the task can finish without delaying the project finish.The difference between early finish and late finish dates determines the amount of slack.
For critical path tasks (tasks that have no slack), the early finish and late finish dates are identical.

Set the slack which defines a task as critical
  1. Choose „Edit” > „Project Options…” or use the Project Options toolbar icon.
  2. Click on the „Calculation” tab and enter the new slack value.
  3. Press „OK” to leave the „Project Options” sheet.
Highlight critical tasks
  1. In the „Format-Info-Inspector” Format-Info-Inspector activate the „Indicate Critical Tasks” check-box.

By default critical tasks are marked red. To use a differnt color change the „Attention” color in the „Format-Info-Inspector” Format-Info-Inspector.

Shorten the critical path
If you want to bring in the project finish date, you need to bring in the dates of your critical path tasks. This is also known as crashing a project.
To do this:

  • Shorten the duration or work on a task on the critical path.
  • Change a task constraint to allow for more scheduling flexibility.
  • Break a critical task into smaller tasks that can be worked on simultaneously by different resources.
  • Revise task dependencies to allow more scheduling flexibility.
  • Set lead time between dependent tasks where applicable.
  • Schedule overtime.
  • Assign additional resources to work on critical path tasks.

If you bring in the dates of your critical path, a different series of tasks could become the new critical path.
There is always one overall critical path for any project schedule. The new critical path would then become the series of tasks you track more closely to ensure the finish date you want.