Virtual Log File (Sanal Günlük Dosyası)

The internal logical management unit within a transaction log (LDF) file. Excessive VLF counts degrade log write throughput, recovery time, and replication speed.

Internal Architecture Breakdown

High VLF fragmentation occurs when autogrowth increments are set too small (e.g. 1MB or 10%), generating thousands of micro-VLFs. This severely impairs database startup recovery times, Always On AG replication synchronization, and log backup performance.

Healthy VLF counts typically range between 50 and 200 depending on log size. Counts exceeding 1,000 represent an immediate performance hazard.

Production Inspection Queries

SQL Server

DBCC LOGINFO; -- Status 2 = aktif VLF, toplam satır sayısı >200 ise log shrink ve kontrollü filegrowth ile düzeltilmelidir.
-- Alternatif DMV (SQL 2017+):
SELECT total_vlf_count, active_vlf_count FROM sys.dm_db_log_stats(DB_ID());

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