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Power BI Refresh Error:
233

What does this error mean?

The connection was established but dropped before it could complete — often caused by shared memory protocol issues or authentication failures after handshake.

Common causes

  • 1Shared memory or Named Pipes connection dropped immediately after establishment
  • 2SQL Server max connections limit reached
  • 3Authentication failure during the TDS login handshake

How to fix it

  1. 1Step 1: Check if the issue is protocol-specific — in SQL Server Configuration Manager, disable Shared Memory and force TCP/IP for all connections.
  2. 2Step 2: Check the SQL Server error log for concurrent connection issues: SELECT @@MAX_CONNECTIONS, (SELECT COUNT(*) FROM sys.dm_exec_sessions) as current_connections;
  3. 3Step 3: Ensure SQL Server Authentication is enabled if a SQL login is used — error 233 can mask auth failures when the handshake breaks before a proper 18456 is raised.

Frequently asked questions

Why does error 233 appear only sometimes?

Intermittent 233 errors often indicate a max connections race condition — the server is near its connection limit and occasionally rejects new connections. Monitor sys.dm_exec_sessions.

Does error 233 appear in Azure SQL Database?

Less commonly — Azure SQL uses TCP/IP only and handles connection limits differently. Error 233 is more characteristic of on-premises SQL Server with Shared Memory enabled.

How do I disable Shared Memory in SQL Server?

Open SQL Server Configuration Manager → SQL Server Network Configuration → Protocols for <instance> → right-click Shared Memory → Disable → restart the SQL Server service.

Official documentation: https://learn.microsoft.com/en-us/sql/relational-databases/errors-events/mssqlserver-233-database-engine-error

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