Issue

Due to the size and complexity of the organization, the migration must be executed in manageable "waves," with each wave containing approximatively 4000 users (no more than 5,000).

A key challenge is ensuring business continuity and minimizing disruption, while also accommodating specific group preferences and technical constraints.

Background & Context

• Wave Structure: The migration is divided into four personal data waves (1-4) and one wave of shared data (5).
• Stakeholder Involvement: The proposal was validated in the Business Steerco on February 17th, with input from business representatives and leadership teams.
• Industrial sites working during weekends: Identified as critical operation, with specific concerns on Composite Materials side - requires dedicated migration batches for sub-populations during cutover weekends, to limit the soft data freeze period.

Wave preparation process

Assumptions

General assumptions:

• March 2026 update: Oil & Gas are out of scope of the migration due to the ongoing carve-out
• Decided in Business Steerco on 17/02/26: no hybrid approach will be considered with sites populated by many different functions: Silex to link with IT, Aubervilliers to link to Novecare & Aroma, Explorer ...
• Decided in Business Steerco on 17/02/26: VIPs will be migrated along with their GBUs, not separately

Migration schedule assumptions:

• To be considered in the beginning of the migration:
  • IT (already heavily involved in pilots + typical first wave population & able to support their peers)
  • One Composite site of 80 pax as part of the first or second wave? (suggestion from the business representative)
• In the middle:
  • Specialty Polymers (filling one full wave because of its size)
• At the end:
  • Composite materials (they have the most specificities & critical data)

Constraints

• Approx people per wave = 4000 (not more than 5000)
• Data volume = 3 weeks of pre-staging per wave minimum (i.e. historical data pre-migration) 
• First Wave preferably smaller (either in amount of user/data, and/or in complexity)
• Ex: users with special characters in the documents names or email titles typically generate more migration errors
• Shared resources wave:
• Watchpoint on integrated mailboxes that have to be reconfigured during the cutover weekend
• Shared drives renaming will be frozen from beg. of April until their migration mid June
• Specific to Organizations:
• GBS & related functions, especially Financen= not at the end of a month (closing)
• Requirement from GBS LT: Finance, HR & Procurement BSA's should be in the GBS Wave

Impacts

• Mixed use of GWS and M365 across organization ("coexistence").
• Duration: ~4 weeks until shared data is migrated.
• Potential collaboration and communication challenges, mitigated by extensive change management efforts.
• Increased IT support demand.

Options considered

Option 1: 

Option 2:

Option 3:

See also

The following section describes relevant documentation: