Cloud migration glossary
110 migration terms explained in plain English, with links to the guides that use them.
A
- A record
A DNS record that points a host name to an IPv4 address. Changing the A record for a website is how traffic moves to a new host.
- Accepted domain
A domain an email system is configured to receive mail for. A domain must be added and verified in the target before mailboxes can use addresses in it.
- AD FS
Active Directory Federation Services: a Windows Server role that provides federated sign-in to cloud and web applications using on-premises Active Directory. Many organisations are moving its sign-in to Microsoft Entra ID to remove the on-premises servers.
- Autodiscover
The service Outlook and mobile mail apps use to find a mailbox's server settings automatically from the email address. It relies on DNS, so the Autodiscover record must point to the right system after a migration or Outlook may connect to the old one.
- AWS Application Migration Service (MGN)
AWS's service for rehosting servers to Amazon EC2. It continuously replicates source servers using an agent, then lets you launch test and cutover instances. AWS documentation now calls it AWS Transform MGN.
- AzCopy
Microsoft's command-line tool for copying files to, from and between Azure Storage accounts. It supports resuming interrupted jobs and copying only changed files.
- Azure Migrate
Microsoft's hub for discovering, assessing and migrating servers, databases and web apps to Azure. Discovery of on-premises servers uses an appliance deployed in the source environment.
- Azure SQL Managed Instance
A deployment option of Azure SQL that provides near-complete compatibility with SQL Server, including SQL Agent and cross-database queries, with patching and backups managed by Microsoft.
B
- BadItemLimit
An older Exchange move setting that sets how many corrupt items a mailbox move may skip before failing. Exchange Online now uses the Data Consistency Score to judge skipped items instead.
C
- Canonical URL
The preferred address of a page, declared with a
rel="canonical"link tag, that tells search engines which URL to index when the same content is reachable at several addresses.- Change Advisory Board (CAB)
A group that reviews and approves planned changes to production systems. Migration cutovers usually need CAB approval, with the plan, risk assessment and rollback steps submitted in advance.
- Change data capture (CDC)
Reading a database's inserts, updates and deletes as they happen, usually from its transaction log, and applying them to a target. CDC keeps the target in sync so the cutover outage is short.
- Cloud Solution Provider (CSP)
Microsoft's programme for partners that sell and manage Microsoft cloud subscriptions for customers. A tenant bought through a CSP partner has its billing and often its admin access managed by that partner.
- CNAME record
A DNS record that makes one host name an alias of another, such as pointing
autodiscover.contoso.comto a provider's host name. A name with a CNAME cannot hold other record types.- Coexistence
A period when the source and target systems both run and work together, with mail routing, address lists and calendar sharing between them. Coexistence lets users move in waves instead of all at once.
- Conditional Access
Microsoft Entra ID policies that allow, block or add requirements to sign-ins based on signals such as user, device, location and app. Review these policies before migration so service accounts and migration tools are not blocked.
- Cross-tenant mailbox migration
Microsoft's native method for moving Exchange Online mailboxes directly between two Microsoft 365 tenants, using a trust set up between the tenants and mail users pre-created in the target.
- Cross-tenant synchronisation
A Microsoft Entra ID feature that automatically creates and updates user accounts from one tenant in another, so people can collaborate across organisations. It is configured with cross-tenant access settings in both tenants.
- Cutover
The point when users and services switch from the source system to the target, for example when MX records are changed or users start signing in to the new tenant. After cutover the target is the system of record.
- Cutover migration
An Exchange migration method that moves all mailboxes to Exchange Online in a single batch, then switches mail flow. It suits small organisations that do not need a period of coexistence.
D
- Data Consistency Score (DCS)
A rating Exchange Online gives a mailbox move based on the type and number of items it could not move, graded Perfect, Good, Investigate or Poor. Moves with a low score need an administrator to review and approve the skipped items before completion.
- Data Migration Assistant (DMA)
A Microsoft tool that checks SQL Server databases for compatibility issues and unsupported features before moving them to a newer SQL Server or Azure SQL.
- Data Migration Service (Google Workspace)
Google's built-in tool in the Admin console for moving email, calendar and contacts into Google Workspace from other mail systems and from other Google accounts.
- Data residency
The physical location, by country or region, where a provider stores your data. Many cloud services let you choose or confirm the region when the tenant or resource is created.
- Data sovereignty
The principle that data is subject to the laws of the country where it is stored or processed, and in some cases the country of the provider. It is broader than residency because it covers who can legally compel access to the data.
- Database Migration Service (DMS)
A managed service that moves databases to the cloud with minimal downtime, by copying existing data and then replicating ongoing changes. AWS and Azure each offer one under this name.
- Delta sync (incremental sync)
A follow-up pass that copies only items created or changed since the previous pass. Running delta syncs keeps the target close to the source so the final pass at cutover is short.
- DKIM
DomainKeys Identified Mail: a method that signs outgoing email with a private key so receivers can check it with a public key published in DNS. Each sending service needs its own DKIM keys set up.
- DMARC
Domain-based Message Authentication, Reporting and Conformance: a TXT record that tells receivers what to do with mail that fails SPF and DKIM alignment checks, and where to send reports.
- DNS cutover
The planned change of DNS records, such as MX, Autodiscover or website records, that sends traffic to the new system. It is often the single step that makes a migration live.
- DNS propagation
The time it takes for a DNS change to be seen everywhere, as cached copies of the old record expire according to their TTL. During propagation some users reach the old destination and some the new.
E
- eDiscovery
Searching, holding and exporting electronic content for legal, audit or investigation purposes. Before a migration, check whether any open cases or holds must be preserved in the source or recreated in the target.
- End of support
The date after which a vendor stops providing security updates, fixes and technical help for a product. Software past end of support still runs but becomes a growing security and compliance risk.
- Enterprise Agreement (EA)
A multi-year volume licensing contract that Microsoft signs directly with large organisations. Most small and medium businesses do not have one: they buy Microsoft 365 through a reseller or partner (the Cloud Solution Provider program, CSP), online from Microsoft, or through a host such as GoDaddy. Some Microsoft add-ons are sold only to Enterprise Agreement customers, for example the Cross-Tenant Shared Data Migration licence for Microsoft's built-in tenant-to-tenant SharePoint site move. If you are not on an Enterprise Agreement, plan on a third-party migration tool instead.
- Extended Security Updates (ESU)
A Microsoft programme that provides critical and important security updates for some products for a limited time after end of support. ESU does not include new features or general fixes; check Microsoft's current terms and eligibility.
F
- Federation
A trust where one identity provider handles sign-in for another service. With a federated domain, Microsoft 365 redirects users to the organisation's own identity provider, such as AD FS or a third-party service, to authenticate.
- Free/busy
Calendar availability information that shows when a person is free or busy without showing meeting details. During coexistence, free/busy lookups between the source and target need specific configuration to work.
G
- GDAP
Granular delegated admin privileges: the Microsoft partner model that gives a partner specific, time-limited admin roles in a customer tenant instead of broad standing access. Partner relationships must be re-established in a new tenant.
- Go/no-go
A decision point shortly before cutover where the team checks agreed criteria, such as sync status, test results and staff availability, and decides whether to proceed or postpone.
- Google Takeout
A Google service that exports a copy of an account's data, such as Gmail and Drive, as downloadable archives. Administrators can use a related data export tool for the whole organisation.
- GWMMO
Google Workspace Migration for Microsoft Outlook: a Google desktop tool that lets a user import mail, calendar and contacts from Outlook profiles or PST files into their Google Workspace account.
H
- Hard match
How directory sync links an on-premises user to a cloud user by setting the cloud user's ImmutableId to the value derived from the on-premises source anchor. It is more precise than a soft match and is used when a soft match fails or is blocked.
- Hardware hash
A unique identifier generated from a Windows device's hardware, used to register it with Windows Autopilot. It can be exported with a PowerShell script or captured by the device manufacturer or reseller.
- Hybrid Configuration Wizard (HCW)
Microsoft's tool that configures a hybrid deployment between on-premises Exchange and Exchange Online, including connectors, organisation relationships and the migration endpoint.
- Hybrid deployment
A configuration that connects on-premises Exchange with Exchange Online so the two act as one organisation, with shared mail routing, address book and mailbox moves. Full hybrid supports long-term coexistence including free/busy; minimal hybrid sets up only what is needed to move mailboxes quickly.
- Hyper-V
Microsoft's hypervisor, built into Windows Server and some editions of Windows, for running virtual machines.
- Hypercare
A period of extra support straight after go-live, when the project team stays available to fix problems quickly before handing over to normal support.
I
- IMAP migration
Copying email from a source server using the IMAP protocol. It moves mail folders only, not calendars, contacts or tasks, so those need a separate export and import.
- ImmutableId (source anchor)
The attribute that permanently ties a synchronised cloud user to its on-premises Active Directory account. It is usually derived from the on-premises object's
ms-DS-ConsistencyGuidorobjectGUID.
L
- Landing zone
A pre-built cloud environment that workloads move into, with accounts or subscriptions, networking, identity, security controls, logging and governance already set up. Building the landing zone first means migrated workloads arrive in a controlled place.
- Litigation Hold
An Exchange setting that preserves all content in a mailbox, including deleted and edited items, so it can be searched for legal or regulatory reasons. Holds must be planned before a migration because they affect what can be removed and moved.
M
- Mail forwarding
Automatically sending a copy of incoming mail from one mailbox to another address. It can bridge a gap during migration, but forwarded mail may fail SPF checks at the receiving end.
- Mail user (mail-enabled user)
A directory object with an email address that has no mailbox in this organisation; mail sent to it is forwarded to an external address. Mail users are pre-created in the target tenant before a cross-tenant mailbox move.
- Microsoft Entra Cloud Sync
A lighter alternative to Entra Connect where configuration lives in the cloud and lightweight provisioning agents run on premises. It suits simpler or multi-forest environments; check Microsoft's comparison for features it does not support.
- Microsoft Entra Connect
Microsoft's server-based tool that synchronises users, groups and passwords from on-premises Active Directory to Microsoft Entra ID. It is installed on a Windows server joined to the domain.
- Migration batch
A group of mailboxes moved together in Exchange Online, created in the Exchange admin center or with PowerShell. Each batch can be started, synced, completed and monitored on its own.
- Migration endpoint
A stored connection in Exchange Online that holds the address, settings and credentials of the source system (such as an Exchange server, IMAP server or Google Workspace) used by migration batches.
- Migration Manager
A migration service in the SharePoint admin center that manages file share migrations across many agents from one place, and also moves content from some other cloud storage services.
- Multifactor authentication (MFA)
Signing in with two or more kinds of proof, such as a password plus an authenticator app or security key. Migrated users often need to register MFA again in the target system.
- MX record
A DNS record that tells sending servers which mail servers accept email for a domain. Changing MX records is the step that switches incoming mail to a new provider.
N
- Nameserver
A server that holds a domain's authoritative DNS records. The registrar records which nameservers are authoritative, so changing nameservers moves control of every DNS record at once.
O
- OneDrive Known Folder Move (KFM)
A OneDrive feature that redirects Windows folders such as Desktop, Documents and Pictures into OneDrive so they sync and are backed up. It is often turned on during a migration to move local files off PCs.
- OST file
An offline Outlook data file (
.ost) that caches a copy of a mailbox on the computer. It is tied to one profile and mailbox and cannot be imported elsewhere; Outlook rebuilds it after a migration.
P
- Pass-through authentication (PTA)
A sign-in method where Microsoft Entra ID passes password checks to agents running on premises, which validate them against Active Directory. Passwords are not stored in the cloud, but sign-in depends on the agents being available.
- Password hash synchronisation (PHS)
A sign-in method where a hash of each user's on-premises password hash is synchronised to Microsoft Entra ID, so users sign in to the cloud with the same password and authentication happens in the cloud.
- Path length limit
The maximum number of characters allowed in a file's full path, including folder and file names. Deep folder trees from file servers can exceed the target's limit, so check paths before migrating and shorten them where needed.
- Pilot
A small first migration, usually of IT staff and willing users, run before the main waves. It tests the tooling, the runsheet and the user communications on real accounts.
- Proxmox VE
An open-source virtualisation platform based on Debian Linux that runs KVM virtual machines and LXC containers, managed through a web interface. It is a common alternative to VMware for smaller environments.
- Proxy address
An email address attached to a mailbox or user. The primary address (shown as uppercase
SMTP:) is used for sending; secondary addresses (lowercasesmtp:) are aliases that also receive mail.- PST file
An Outlook data file (
.pst) that stores a copy of email, calendar and contacts on a local disk. PST files are used to export and import mailbox data, and to archive old mail.
R
- RAID log
A project register of Risks, Assumptions, Issues and Dependencies (some teams use Decisions). Each entry has an owner and a status so nothing that could derail the migration is forgotten.
- Refactor
Changing an application's code or architecture so it runs well on the target platform, for example breaking it into services or moving to serverless. It takes the most effort and gives the most control over the result.
- Registrar
The company through which a domain name is registered and renewed. The registrar is often, but not always, also the DNS host.
- Rehost (lift and shift)
Moving a server or application to new infrastructure, usually the cloud, without changing its code or architecture. It is the fastest strategy but carries existing inefficiencies across with the workload.
- Relocate
Moving workloads to a cloud-hosted version of the same platform without converting each machine, for example moving VMware virtual machines to a VMware environment run by a cloud provider. The hypervisor stays the same, so virtual machines are not rebuilt.
- Replatform
Moving an application with a few targeted changes to use a managed service, such as moving a self-managed database to a managed database service, while keeping the core application the same.
- Replication
Continuously copying a server's disks or a database's changes to the target, so the target stays close to current until cutover.
- Repurchase
Replacing an application with a different product, usually a software-as-a-service (SaaS) offering, and migrating the data into it. Moving from on-premises Exchange to Exchange Online, or from desktop accounting software to a cloud ledger, are examples.
- Retain
Deliberately keeping a workload where it is for now, because it is not ready, not worth moving or tied to constraints such as licensing or compliance. Retained workloads are reviewed again later.
- Retention policy
A rule that keeps content for a set period, deletes it after a set period, or both. Retention applies to the tenant where it is set, so it does not travel with data to a new tenant or platform.
- Retire
Switching off an application or server that is no longer needed instead of migrating it. Retiring unused systems early reduces the scope, time and risk of the migration.
- Rollback
Returning to the source system after a failed or partial cutover. A rollback plan states the trigger for rolling back, the steps, and the point after which rolling back is no longer practical.
- RPO (recovery point objective)
The maximum amount of data, measured in time, that the business can afford to lose if a system fails. It sets how often data must be backed up or replicated.
- RTO (recovery time objective)
The maximum time a system can be unavailable before the impact is unacceptable. In a migration it sets how long the cutover window and any rollback can take.
- Runbook
A documented, repeatable procedure for a technical task, with exact steps, commands and expected results. A migration runbook describes how to perform each type of move so anyone on the team can follow it.
- Runsheet
A time-ordered list of every action in a cutover, with owner, start time and status for each step. It is the script the team follows on the night and the record of what was done.
S
- Search Console change of address
A tool in Google Search Console that tells Google a site has moved to a new domain. It is used after 301 redirects are in place and both properties are verified.
A Google Drive space owned by the organisation rather than one person, so files stay when members leave. Shared drives usually map to SharePoint sites or Teams in a move to Microsoft 365.
A mailbox several people can open, such as info@ or accounts@, that has no sign-in of its own. Converting a departed user's mailbox to a shared mailbox keeps its mail accessible.
- SharePoint Migration Tool (SPMT)
Microsoft's free desktop tool for moving files from file shares and SharePoint Server to SharePoint, OneDrive and Teams. It runs on a Windows computer that can reach the source.
- Soft match
How directory sync links an on-premises user to an existing cloud user by matching the primary SMTP address or UPN. It is used when cloud accounts already exist before sync is turned on.
- SPF
Sender Policy Framework: a TXT record that lists the servers allowed to send email for a domain. A domain should have only one SPF record, so add the new provider to the existing record during migration instead of creating a second one.
- Staged migration
An older Exchange migration method that moves mailboxes in groups while on-premises accounts are synchronised to Microsoft 365. It applies only to very old Exchange versions; current versions use hybrid instead.
- Staging site
A private copy of a website used to build and test changes before they go live. During a migration the new site is usually built on staging and checked before DNS is changed.
T
- Tenant
A dedicated instance of a cloud service, such as Microsoft 365 or Google Workspace, that holds one organisation's users, domains, data and settings. Each tenant has its own directory and administrators.
- Tenant-to-tenant migration
Moving users, mailboxes, files, Teams and domains from one tenant to another, usually after a merger, acquisition or divestment. Domains can only be verified in one tenant at a time, so the domain move is a key cutover step.
- Test failover
Starting a copy of a replicated server in an isolated network to check it boots and works, without affecting the source or ongoing replication.
- Throttling
Limits a service applies to how fast a tool can read or write data, to protect performance for everyone else. Throttled migrations slow down or pause, so plan for it when estimating duration and run large copies outside business hours where the vendor recommends.
- TTL (time to live)
The number of seconds resolvers may cache a DNS record before checking again. Lowering the TTL in advance of a change makes the switch take effect faster once you make it.
- TXT record
A DNS record that holds text, used to prove domain ownership to a provider and to publish email authentication policies such as SPF and DMARC.
U
- User acceptance testing (UAT)
Testing by the people who will use a system, to confirm it works for their real tasks before go-live. In a migration, UAT checks that mail, files, apps and permissions behave as expected in the target.
- User principal name (UPN)
The sign-in name of a user in Active Directory and Microsoft Entra ID, formatted like an email address, for example
user@contoso.com. Keeping the UPN the same as the primary email address avoids sign-in confusion.
V
- Version history
Earlier saved copies of a file kept by the storage service. Migration tools may move all, some or none of the versions, which affects copy time and storage used in the target.
- VMware Cloud Foundation (VCF)
Broadcom's full private cloud stack combining vSphere compute, vSAN storage, NSX networking and management tools, sold as one product. Changes to VMware licensing have led many organisations to review alternatives.
- VMware vSphere
VMware's server virtualisation platform, made up of the ESXi hypervisor and vCenter Server for central management.
W
- Wave
A group of users, mailboxes, sites or servers that migrate together in one scheduled window. Large migrations are split into waves so each one is small enough to test, support and roll back.
- Windows Autopilot
A Microsoft service that sets up and enrols new or reset Windows devices into Intune and Entra ID straight from the box. Devices are registered with their hardware hash, and a device can be registered to only one tenant at a time.
- WP-CLI
The command-line interface for WordPress, used to manage plugins, users and settings and to run tasks such as database exports and URL search-replace.