Dissolve Removes an Activity and Joins Its Predecessors to Its Successors

What a planner means

Dissolve (Edit > Dissolve in Professional) is a command. It is not Delete, not Link Activities, not Unlink Activities, not a TASKPRED row, not a relationship type, and not a milestone. Oracle: "Dissolving an activity removes the dissolved activity and joins the dissolved activity's predecessor and successor activities as well as possible to maintain the project's network logic." You cannot dissolve an activity unless it has a predecessor and a successor.

Professional Delete tip (Oracle): "To remove an activity, but maintain the relationship between its predecessor and successor activities, dissolve the activity instead of deleting it." Delete is Edit > Delete. See TASKPRED (Activity Relationships) and FS / SS / FF / SF + Lag (Planner Language) for the links themselves. See Start vs Finish Milestones for start/finish milestones.

Professional — Activities window. Oracle Edit Menu: Dissolve "Deletes the selected activity and joins its predecessor and successor activities with a finish to start relationship. This command is enabled when you select an activity that has a predecessor and successor." Edit Toolbar: same one-liner; corresponding menu Edit > Dissolve; Activities only; icon not shown by default. Link Activities is a separate Edit command (finish-to-start between the activities you select, in list order). Unlink Activities "Removes relationships between the selected activities."

Oracle's Dissolve an activity page does not stop at finish-to-start. It prints a first-half / second-half combination rule:

• The first half of the relationship between the immediate predecessor and the dissolved activity is used as the first half of the new relationship to all successors that had a relationship with the dissolved activity.
• The second half of each new relationship "remains the same for each successor as when each was linked to the dissolved activity."

Oracle's example (Activity B dissolved; A was linked to B with SF):

Do not collapse the Edit Menu "finish to start" sentence and this combination example into one rule. Oracle printed both. The Dissolve page's example uses one immediate predecessor and several successors. Oracle did not print a worked example with several predecessors.

Lag (Oracle Dissolve page and Calculations tab):

• Default: "any lag applied to relationships with the dissolved activity is removed and the new relationships created have zero lag."
• Retain lag on the Calculations tab of User Preferences: "the lag from the predecessor relationship is added to the lag from the successor relationship and applied to the new relationship." The Calculations tab heading as published is Regain lag; the body says "retain the lag." If the option is not selected, "the newly created relationship has zero lag."

User Preferences are not a project XER table.

EPPM web — Oracle published Dissolving Activities: "remove the dissolved activity and join the predecessor and successor activities to maintain the project's network logic." You cannot dissolve unless it has a predecessor and successor. "You can only dissolve one activity at a time." Menu on that page: select a single activity, Actions > Dissolve, Confirm Yes, Save. Retain lag is "in the General section in the Global tab of the My Preferences page" with the same pred-lag-plus-succ-lag sentence. The EPPM page fetched does not print the Professional first-half / second-half combination rule, the SF/FF/FS/SS example, or Edit > Dissolve. Do not copy those Professional sentences onto EPPM as if Oracle printed them there.

XER

Dissolve is a command. It is not an XER table. After it runs you see a missing TASK row and rewritten TASKPRED rows. Do not invent a DISSOLVE / DISSOLV table.

Oracle's project XER data map TOC lists no DISSOLVE, DISSOLV, or DISSOLVED table. Oracle did not name an XER column for Retain lag / Regain lag (that is a User Preference / My Preferences option).

A Viewer parse of one XER cannot reconstruct whether the planner used Dissolve or Delete, or whether Retain lag was on.

Microsoft Project

Desktop Project has no Dissolve command on the pages fetched.

Microsoft documents Delete (task IDs update when you delete a task), Unlink Tasks ("Removing a task link removes the dependency between two tasks"), and Inactivate (Project Professional: the task "stays in the project plan, but does not affect resource availability, the project schedule, or how other tasks are scheduled"). Microsoft Active field: "Unlike deleted tasks, inactive tasks are recoverable." Reactivated tasks "retain any dependencies, constraints, or resource assignments associated with them."

Microsoft Autolink inserted or moved tasks links a new task between already-linked tasks. That is insert, not remove. It is not Dissolve.

The pages fetched do not print a Microsoft command that removes a task and joins its predecessors to its successors the way Oracle Dissolve does. Do not map P6 Dissolve to MSP Delete, Unlink Tasks, Inactivate, or Autolink and call them the same command. Do not claim MPXJ can write a real MPP.

Don't

• Treat Dissolve as Delete, as Link Activities, as Unlink Activities, as a TASKPRED row, as a relationship type, or as a milestone.
• Invent a DISSOLVE / DISSOLV XER table, or treat Retain lag as a TASKPRED / SCHEDOPTIONS / PROJECT column.
• Copy Professional Edit > Dissolve / Edit Toolbar / first-half–second-half combination onto EPPM as if Oracle printed those there.
• Collapse Oracle's Edit Menu "finish to start" one-liner and the Dissolve page's combination example into one invented rule.
• Invent how several predecessors combine; Oracle's worked example has one immediate predecessor.
• Map Dissolve to MSP Delete, Unlink Tasks, Inactivate, or Autolink as the same command.
• Claim MPXJ writes a real MPP.
• Claim a Viewer reconstructed that the planner last used Dissolve, or the Retain lag setting, from an XER.