Azure SQL automatic index compaction: lower your fill factor under continuous inserts
Does Azure SQL automatic index compaction fix UUIDv7 page density? Yes after a load, but with continuous inserts it needs a fill factor below 100.
SQL Server
Microsoft SQL Server in practice: installation, Always On availability groups, backup and restore, performance tuning, security, PowerShell automation, SQL Server on Linux and upgrades.
SQL Server 2025: is optimized locking really working? Ask the Extended Events
How to check what SQL Server 2025 optimized locking really does with Extended Events: escalations, LAQ attempts and restarts.
SQL Server: Disabling FileTable/FileStream on an AlwaysOn high-availability instance
Contexte A customer recently asked me to disable FileTable/FileStream on their instance because the databases no longer use it, and to ensure that this is indeed the case.The aim is to migrate to a new architecture without FileTable/FileStream in a second time. Link to FileTable and FileStream if you need to know a bit more about these technologies The environment…
Calling AI from SQL Server 2025 can lock everyone out of your on-prem instance
sp_invoke_external_rest_endpoint has no limit in SQL Server 2025: each waiting call holds a worker. Compared with Azure SQL.
Archiving 5 TB from Oracle into SQL Server: views, indexes and compression (part 2)
Translating 4,000 Oracle views, rebuilding indexes offline on Standard Edition, and compressing clustered index to save 1T.
SQL Server 2025 CU5: max lock manager cache memory (%): what I could reproduce and what I could not
Cumulative Update 5 for SQL Server 2025 was released on May 20, 2026 (build 17.0.4045.5). Seven entries in the KB, mostly fixes. One of them is not a fix: it is a new server configuration option, max lock manager cache memory (%). Reference: https://support.microsoft.com/en-us/servicing/sql/sql-server-2025/cumulative-update/kb5084896-cu5 I built a lab on CU5 and on later builds up to CU9 and I spent…
Archiving 5 TB from Oracle into SQL Server: a migration logbook (part 1)
Loading 5 TB from Oracle into SQL Server with SSMA: type overflows, heaps, and the settings that took 788 rows/s to 42,170.
SQL Server: why can’t I read the full table in parallel???
Why SQL Server keeps a full SELECT * serial: I/O cost is never divided across threads. Forcing parallelism burned 3x the CPU.
SQL Server: Stop ordering index columns by selectivity
Column order does not affect equality seeks in SQL Server. Measured on 5M rows, then proven inside the B-tree pages.
Why UUIDv7 does not reduce fragmentation in SQL Server
UUIDv7 places its timestamp first, but SQL Server compares uniqueidentifier
values starting from the last bytes. Measured on 25,000 inserts: no gain over NEWID().
Fixing ORA-00904 on Oracle hidden columns during SSMA data migration
SSMA fails with ORA-00904 on Oracle SET UNUSED columns. Fix it with a custom select aliasing NULL, no source DDL required.
When tempdb write latency points below SQL Server
During a recent performance review on a SQL Server 2019 instance (AlwaysOn Failover Cluster Instance, bare-metal), one number stood out. This post follows the investigation: from a latency figure in a DMV, down the I/O path to a RAID controller setting nobody had ever chosen. The starting point: one number from a health check The I/O statistics of the instance…