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What is log send queue size?
THere is a performance counter for Always-on Log Send Queue. The amount of log records in the log files of the primary database, in kilobytes, that are not yet sent to the secondary availability replica.
What is redo queue size?
The Availability Group Redo Queue Size (KB) alert indicates the amount of log records from log files in KB that need redoing in the secondary replica to complete synchronization. Alert includes affected databases. For more information on configuring alerts and setting thresholds, see Configure alerts.
What is redo queue?
The redo queue is the queue of log records on the mirror, log records that have already been hardened on the principal and mirror and only need to be redone (against the data file) on the mirror. The redo queue must be completely redone before the mirror comes online.
What is redo thread in always on?
If the total number of required threads for a single instance exceeds 100, SQL Server uses a single redo thread for every remaining database. Serial Redo threads are released after ~15 seconds of inactivity.”
What is redo rate?
Display Name: Average Redo Rate across all Secondary Replica Databases. Description: Average rate at which the log records are being redone across all secondary replica databases, in kilobytes (KB) per second.
How do you turn off redo in parallel?
If you are experiencing this wait type as one of the highest waits on your AG secondaries, you can disable parallel redo by turning on trace flag 3459 using DBCC TRACEON (3459, -1), or adding it as a startup trace flag using the Configuration Manager.
What is redo thread?
The redo log file groups of an instance are collectively called a thread, or more appropriately, a redo log thread. Each instance has its own redo thread. The redo log groups function in a true circular fashion; as one fills up, another redo log records the redo entries.
What is parallel redo?
In SQL Server 2016, the redo model was enhanced with multiple parallel redo worker threads per database to share the redo workload. In addition, each database has a new helper worker thread for handling the dirty page disk flush IO. This new redo model is called parallel redo .
How do I change the size of my redo log?
select group#, status from v$log; You may have to run the alter command up to three times to get group 1 to be CURRENT. Repeat steps 1 to 7 for group 2, group 3, and group 4. Confirm the size change to each group is now 165 Mb.