Monitor and Optimize an Analytics Solution · Topic 3 of 5

Resolving Eventhouse, Eventstream, T-SQL and OneLake Shortcut Errors

DP-700 troubleshooting: Eventhouse ingestion failures and query limits, Eventstream runtime logs, warehouse T-SQL errors, and broken OneLake shortcuts.

5 min

In a nutshell

.show ingestion failures lists failed ingestions with a transient or permanent kind.
KQL results are truncated at 500,000 records or 64 MB by default.
Eventstream: data insights for counts, runtime logs for errors, and publish after edits.

What it is

Real-time items, SQL engines and shortcuts fail differently from batch jobs. A stream can run while silently dropping events, a T-SQL statement can hit an unsupported feature, and a shortcut breaks when someone renames its target folder.

Find where data stops, read the message, and fix the cause: format, schema, permissions, credentials or unsupported syntax.

How it works

Eventhouse errors

Failed ingestions are listed by a management command:

.show ingestion failures
| where FailedOn > ago(1d)
| project FailedOn, Table, ErrorCode, FailureKind, Details

Symptom	Likely cause	Fix
Ingestion failures, or rows with empty columns	Ingestion mapping does not match the incoming JSON or CSV fields	Correct the ingestion mapping or the data format
Data appears with a delay	Ingestion batching waits to collect data	Adjust the batching policy, or use streaming ingestion for low latency
Query result is cut off	The default result limit of 500,000 records or 64 MB	Filter or aggregate; avoid `set notruncation` for large results
Query fails on memory or runs very long	Query scans too much data or joins large tables badly	Filter by time first, project fewer columns, summarize before joining
Old data missing	It aged out under the retention policy	Extend retention, or keep history in OneLake

FailureKind shows whether a failure is Transient (a retry may succeed) or Permanent (the data or mapping must change).

Eventstream errors

Where	What it shows
Data insights	Incoming and outgoing event counts per node
Runtime logs	Errors, warnings and information for sources, operators and destinations
Node status	Whether a source or destination is active or has failed

Symptom	Likely cause	Fix
No incoming events	Wrong connection string or key, or another reader using the same Event Hubs consumer group	Fix the connection; give the eventstream its own consumer group
Events come in but none reach the destination	Format mismatch (JSON, CSV or Avro), or an operator filters everything out	Set the correct data format; test operators in the editor
Destination errors	Eventhouse table or lakehouse table schema does not match the events	Align the schema or mapping
Changes have no effect	The eventstream was edited but not published	Publish the changes

T-SQL errors

Symptom	Likely cause	Fix
`INSERT` or `UPDATE` fails on a lakehouse	The SQL analytics endpoint is read-only	Write with Spark, or load into a warehouse
`CREATE TABLE` fails on a data type	Unsupported type in Fabric Warehouse, such as `nvarchar`, `datetime` or `money`	Use `varchar`, `datetime2(6)` and `decimal`
A new lakehouse table is not visible in the endpoint	Metadata sync has not caught up, or the folder is not a valid Delta table	Wait or refresh the endpoint's metadata; check the table format
Permission denied	Missing ReadData, or missing `GRANT`	Grant the item permission or object permission
Update conflict error	Two transactions modified the same table at once under snapshot isolation	Retry the losing transaction; avoid concurrent writes to one table
Cross-database query fails	Three-part names work only for items in the same workspace	Use a shortcut to bring the other item's table into this workspace

-- Fails in Fabric Warehouse: nvarchar and datetime are not supported
-- CREATE TABLE dbo.Customer (Name NVARCHAR(100), Created DATETIME);

CREATE TABLE dbo.Customer
(
    Name    VARCHAR(100) NOT NULL,
    Created DATETIME2(6) NOT NULL
);

OneLake shortcut errors

Symptom	Likely cause	Fix
Shortcut shows an error or no data	Target folder deleted, moved or renamed	Recreate the shortcut to the new path
Works for some users, fails for others	Internal shortcut: those users lack permission on the target	Grant them access to the target item
Fails for everyone after working before	External shortcut: connection credentials expired or were rotated	Update the connection
Access denied from cloud storage	The storage account's role assignments or firewall do not allow the identity	Grant the identity a storage data role, or allow access
Shortcut sits under an Unidentified folder in Tables	Target is not a Delta table	Point it to a Delta folder, or create it under Files

A worked example

Analysts report that a KQL dashboard has shown no new data since the morning, but the IoT devices are sending normally.

In the eventstream, data insights shows incoming events but none outgoing, and the runtime logs show deserialization errors. A firmware update had switched the devices from JSON to Avro, so setting the source's data format to Avro and publishing the eventstream restores the flow.

How the exam asks about this

"Find why rows are not being ingested into a KQL table." .show ingestion failures.
"An eventstream receives events but the destination gets none." Check runtime logs and data insights for format or schema errors.
"A shortcut works for the lakehouse owner but not for a Viewer." The Viewer lacks permission on the shortcut's target.

What to remember for the exam

.show ingestion failures lists failed ingestions with a transient or permanent kind.
KQL results are truncated at 500,000 records or 64 MB by default.
Eventstream: data insights for counts, runtime logs for errors, and publish after edits.
Fabric Warehouse does not support nvarchar, datetime or money; the SQL analytics endpoint is read-only.
Internal shortcuts fail per user; external shortcuts fail for everyone when the connection breaks.

Watch out

Rotating a storage key or SAS token breaks every external shortcut that uses that connection at the same moment. Update the connection as part of the rotation.

Common mistakes

Assuming no errors means no data loss in a stream. Mapping or format mismatches can drop or empty fields; compare incoming and outgoing counts.

Running set notruncation to "fix" a truncated result. Filter or aggregate instead.

Granting workspace Contributor to fix a shortcut access error. Grant the user read access on the target item instead.

Check yourself

Which command lists failed ingestions in an Eventhouse?
.show ingestion failures, which includes the error code and whether the failure is transient or permanent.
Why does an UPDATE against a lakehouse table through the SQL analytics endpoint fail?
The endpoint is read-only; lakehouse tables are changed with Spark or loaded into a warehouse instead.
What does an Unidentified folder in a lakehouse's Tables area indicate for a shortcut?
The shortcut target is not a Delta table, so it cannot be registered as a table.

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