SQL Server Error 17803

Error number

17803

Severity

20 (fatal: the connection ends; may indicate a serious problem)

State

Not documented by Microsoft (not reproduced here)

Product

Microsoft SQL Server Database Engine

Versions

All supported SQL Server versions (2016 to 2025), Azure SQL Managed Instance

Category

Memory

Last reviewed

24 October 2026

What it means

Error 17803 means SQL Server could not allocate the small amount of memory it needs to set up a new connection, so it closed that connection; the instance as a whole is short of memory.

Each new connection needs memory for its session structures and network buffers before login can finish. When that allocation fails, SQL Server closes the connection with 17803, and the client sees its connection attempt fail. Microsoft's explanation is simply that the server is running out of memory, and the action is to find out why. The connection that failed is a symptom, not the cause.

The catalogue severity is 20, which marks a problem with the connection being set up rather than with a database. Because it appears before any query runs, 17803 often shows up together with other memory errors such as 701 or 802. Look at memory at the time of the error: what Windows had available, what SQL Server was using, and which internal component had grown.

Common causes

• Pressure from outside SQL Server: other services or applications on the same machine, or a virtual machine whose memory is overcommitted, leaving Windows little to give.
• Max server memory left at its default on a server shared with other workloads, so SQL Server and the operating system compete for the same RAM.
• One engine component using far more memory than usual (large query memory grants, a bloated plan cache, the lock manager).
• Memory used inside the SQL Server process but outside the buffer pool, for example by linked server providers, SQLCLR or third-party DLLs.
• A storm of new connections (for example after an application restart) arriving while memory is already tight.

Diagnose it

Read-only These queries only read metadata and dynamic management views. They do not change data, permissions or configuration, so they are safe to run first.

SELECT total_physical_memory_kb / 1024 AS total_mb,
       available_physical_memory_kb / 1024 AS available_mb,
       available_page_file_kb / 1024 AS available_page_file_mb,
       system_memory_state_desc
FROM sys.dm_os_sys_memory;

SELECT physical_memory_in_use_kb / 1024 AS in_use_mb,
       memory_utilization_percentage,
       process_physical_memory_low, process_virtual_memory_low
FROM sys.dm_os_process_memory;

SELECT committed_kb / 1024 AS committed_mb,
       committed_target_kb / 1024 AS target_mb
FROM sys.dm_os_sys_info;

SELECT TOP (15) type, name,
       pages_kb / 1024 AS pages_mb,
       virtual_memory_committed_kb / 1024 AS vm_committed_mb
FROM sys.dm_os_memory_clerks
ORDER BY pages_kb DESC;

SELECT event_time, oom_cause_desc, available_physical_memory_mb,
       top_memory_clerks
FROM sys.dm_os_out_of_memory_events
ORDER BY event_time DESC;

SELECT name, value_in_use
FROM sys.configurations
WHERE name IN (N'max server memory (MB)', N'min server memory (MB)');

How to fix it

Each fix is labelled with what it changes. Try read-only checks and the least invasive fix first, and test changes outside production.

-- Only with a value chosen from measurements (example: 28 GB on a 32 GB server)
EXEC sp_configure 'show advanced options', 1;
RECONFIGURE;
EXEC sp_configure 'max server memory (MB)', 28672;
RECONFIGURE;

Examples

A new connection is closed while the server is out of memory

Shown as documented by Microsoft; not reproduced here, because it needs real memory exhaustion on the instance. The message text is from sys.messages on SQL Server 2025; the level and state recorded at the time were not observed, so no header is shown.

-- Any new connection, for example
sqlcmd -S ServerName -E -Q "SELECT 1"

There was a memory allocation failure during connection establishment. Reduce nonessential memory load, or increase system memory. The connection has been closed.

How to prevent it

Size the server for its workload and leave headroom for Windows and anything else that runs on it. Set max server memory deliberately on servers that share RAM with other services, and revisit it when the workload or hardware changes.

Monitor available memory, the largest memory clerks and the rate of new connections, so that growing pressure is visible before connections start failing. Connection pooling in the applications also reduces how often new connections have to be set up.

Common questions

Learn more on CodeWithSQL

• Performance tuning

Official documentation

• MSSQLSERVER_17803 (Microsoft Learn)
• Troubleshoot out of memory or low memory issues in SQL Server
• Server memory configuration options
• sys.dm_os_sys_memory

Last technically reviewed 24 October 2026; examples and diagnostics run on SQL Server 2025 (17.0.1145.4). Message text checked against the engine's sys.messages catalogue.