Typo in the login name in the management script: the most frequent cause. A single character difference — trailing space, wrong case on a case-sensitive collation server, underscore vs hyphen — causes the lookup to return zero rows and SQL Server raises 15151 immediately.. The login was already dropped by a prior migration step: idempotent deployment scripts often run DROP LOGIN followed by CREATE LOGIN; if the first run succeeded and the second run repeats the DROP, the login no longer exists and 15151 fires.. The script targets the wrong SQL Server instance: deployment pipelines that parameterise the target server may connect to a dev or staging instance where the login was never created, while the login exists only on production.. The login exists as a Windows or Azure AD principal but the script uses a SQL login name, or vice versa: sys.server_principals distinguishes type 'S' (SQL), 'U' (Windows), and 'E' (Azure AD external). A script referencing [DOMAIN\user] while expecting a SQL login will not match.. The login was created in a different database context or on a linked server: SQL logins are server-scoped, not database-scoped. Executing a management script inside a USE [database] context does not change where logins are looked up, but engineers sometimes confuse server principals with database users and expect a login they created as a database user to be present in sys.server_principals.. A previous failed migration left a partially applied state: if a transaction that created the login was rolled back due to an earlier error in the same batch, the login was never committed. A subsequent run of only the ALTER LOGIN portion of the script fails with 15151 because the CREATE LOGIN never persisted.. Azure SQL Managed Instance or Azure SQL Database scope mismatch: on Azure SQL Database, logins must exist in the logical master database. Scripts executed against a user database that try to ALTER LOGIN will fail with 15151 if the login does not exist in master on the logical server.

Step 1 — Confirm the login exists and check its exact name: SELECT name, type_desc, is_disabled, create_date FROM sys.server_principals WHERE type IN ('S','U','G','E','X') ORDER BY name; Locate the login by scrolling or filtering. Note the exact casing.. Step 2 — Check server collation to understand case sensitivity: SELECT SERVERPROPERTY('Collation') AS server_collation; If the result contains 'CS' (case-sensitive), 'MyLogin' and 'mylogin' are distinct. Match the name exactly as returned by sys.server_principals.. Step 3 — If the login is missing and should exist, create it before re-running the script: For SQL login: CREATE LOGIN [loginname] WITH PASSWORD = 'StrongPass1!', CHECK_POLICY = ON; For Windows/AD login: CREATE LOGIN [DOMAIN\username] FROM WINDOWS;. Step 4 — If the script uses DROP LOGIN idempotently, guard the statement: IF EXISTS (SELECT 1 FROM sys.server_principals WHERE name = 'loginname' AND type IN ('S','U','G','E')) DROP LOGIN [loginname]; This prevents 15151 on repeated pipeline runs.. Step 5 — On Azure SQL Database, verify the login exists in master on the logical server: Connect to the master database, then run: SELECT name, type_desc FROM sys.sql_logins WHERE name = 'loginname'; If absent, create it there before executing the management script against the user database.. Step 6 — Check whether the ADF linked service or pipeline service principal is the account being managed: SELECT name, type_desc FROM sys.server_principals WHERE name = 'your-service-principal-or-mi-name'; If absent, the provisioning step for that identity did not complete. Re-run the provisioning runbook or Terraform/Bicep module.. Step 7 — After fixing, re-run the failed script or pipeline step and verify with: SELECT name, is_disabled FROM sys.server_principals WHERE name = 'loginname'; A row with is_disabled = 0 confirms the login is active and manageable.

Low severityauthentication

SQL Server Error:
15151

Impact

Error 15151 only fires in DDL scripts, not during ADF pipeline execution, so it does not directly stall a running pipeline. It becomes a blocker when the failing script is part of a CI/CD deployment pipeline or provisioning automation: if the ALTER/DROP LOGIN step aborts, downstream steps that depend on that login's permissions may fail, causing linked service tests or actual pipeline runs to produce 18456 or permission-denied errors until the deployment is manually retried.

Because 15151 is a DDL error in a management script, it does not directly interrupt ADF pipeline runs that are already using a valid login. The downstream impact is indirect: if the deployment script fails midway, a permission grant or login modification intended to authorize a service account may not have applied. Subsequent ADF linked service connection tests or pipeline runs that rely on that account will then fail with 18456 (login failed) or 229 (permission denied). There is no automatic retry for DDL scripts — the deployment pipeline must be re-run manually after the login issue is resolved.

What does this error mean?

SQL Server raises error 15151 when a DDL statement — ALTER LOGIN, DROP LOGIN, DISABLE LOGIN, or GRANT SERVER-level permission — references a login name that does not exist in sys.server_principals. This is a server-scoped metadata error, not a connection failure. In a data pipeline context it surfaces during deployment scripts, provisioning automation, or CI/CD pipelines that manage database access. The engineer sees an immediate batch termination with message: "Cannot find the login '%.*ls', because it does not exist or you do not have permission." No data is moved or corrupted — the script simply halted before completing.

Common causes

1Typo in the login name in the management script: the most frequent cause. A single character difference — trailing space, wrong case on a case-sensitive collation server, underscore vs hyphen — causes the lookup to return zero rows and SQL Server raises 15151 immediately.
2The login was already dropped by a prior migration step: idempotent deployment scripts often run DROP LOGIN followed by CREATE LOGIN; if the first run succeeded and the second run repeats the DROP, the login no longer exists and 15151 fires.
3The script targets the wrong SQL Server instance: deployment pipelines that parameterise the target server may connect to a dev or staging instance where the login was never created, while the login exists only on production.
4The login exists as a Windows or Azure AD principal but the script uses a SQL login name, or vice versa: sys.server_principals distinguishes type 'S' (SQL), 'U' (Windows), and 'E' (Azure AD external). A script referencing [DOMAIN\user] while expecting a SQL login will not match.
5The login was created in a different database context or on a linked server: SQL logins are server-scoped, not database-scoped. Executing a management script inside a USE [database] context does not change where logins are looked up, but engineers sometimes confuse server principals with database users and expect a login they created as a database user to be present in sys.server_principals.
6A previous failed migration left a partially applied state: if a transaction that created the login was rolled back due to an earlier error in the same batch, the login was never committed. A subsequent run of only the ALTER LOGIN portion of the script fails with 15151 because the CREATE LOGIN never persisted.
7Azure SQL Managed Instance or Azure SQL Database scope mismatch: on Azure SQL Database, logins must exist in the logical master database. Scripts executed against a user database that try to ALTER LOGIN will fail with 15151 if the login does not exist in master on the logical server.

How to fix it

1Step 1 — Confirm the login exists and check its exact name: SELECT name, type_desc, is_disabled, create_date FROM sys.server_principals WHERE type IN ('S','U','G','E','X') ORDER BY name; Locate the login by scrolling or filtering. Note the exact casing.
2Step 2 — Check server collation to understand case sensitivity: SELECT SERVERPROPERTY('Collation') AS server_collation; If the result contains 'CS' (case-sensitive), 'MyLogin' and 'mylogin' are distinct. Match the name exactly as returned by sys.server_principals.
3Step 3 — If the login is missing and should exist, create it before re-running the script: For SQL login: CREATE LOGIN [loginname] WITH PASSWORD = 'StrongPass1!', CHECK_POLICY = ON; For Windows/AD login: CREATE LOGIN [DOMAIN\username] FROM WINDOWS;
4Step 4 — If the script uses DROP LOGIN idempotently, guard the statement: IF EXISTS (SELECT 1 FROM sys.server_principals WHERE name = 'loginname' AND type IN ('S','U','G','E')) DROP LOGIN [loginname]; This prevents 15151 on repeated pipeline runs.
5Step 5 — On Azure SQL Database, verify the login exists in master on the logical server: Connect to the master database, then run: SELECT name, type_desc FROM sys.sql_logins WHERE name = 'loginname'; If absent, create it there before executing the management script against the user database.
6Step 6 — Check whether the ADF linked service or pipeline service principal is the account being managed: SELECT name, type_desc FROM sys.server_principals WHERE name = 'your-service-principal-or-mi-name'; If absent, the provisioning step for that identity did not complete. Re-run the provisioning runbook or Terraform/Bicep module.
7Step 7 — After fixing, re-run the failed script or pipeline step and verify with: SELECT name, is_disabled FROM sys.server_principals WHERE name = 'loginname'; A row with is_disabled = 0 confirms the login is active and manageable.

Example log output

Msg 15151, Level 16, State 1, Line 3Cannot find the login 'svc_adf_reader', because it does not exist or you do not have permission.The statement has been terminated.

Frequently asked questions

15151 fix — how do I quickly resolve it without re-running the whole migration?

Isolate the failing statement, check sys.server_principals for the correct login name and casing, then either create the missing login with CREATE LOGIN or correct the name in your script. Re-run only the failed step — you do not need to replay earlier steps that already succeeded.

Can 15151 appear when using Azure Data Factory with a Managed Identity?

Not during ADF pipeline execution. ADF uses the Managed Identity at connection time, which raises 18456 or 916 on failure — not 15151. You would see 15151 only in a deployment or provisioning script that runs ALTER LOGIN or DROP LOGIN targeting the Managed Identity's server principal name.

Does 15151 mean the login has no permission, or that it literally does not exist?

Both interpretations are covered by the error message — 'does not exist or you do not have permission' — but in practice 15151 almost always means the login is absent from sys.server_principals. If the login exists and you still get 15151, the executing account lacks ALTER ANY LOGIN or sysadmin rights to manage it.

15151 on DROP LOGIN — how do I make deployment scripts idempotent?

Wrap every DROP LOGIN in an existence check: IF EXISTS (SELECT 1 FROM sys.server_principals WHERE name = N'loginname' AND type IN ('S','U','G','E')) DROP LOGIN [loginname]; This pattern is safe to run multiple times and will not raise 15151 if the login was already removed in a previous deployment.

Source · learn.microsoft.com/en-us/sql/relational-databases/errors-events/database-engine-events-and-errors