SQL Server, Database Replica object

Applies to: yesSQL Server (all supported versions)

The SQLServer:Database Replica performance object contains performance counters that report information about the secondary databases of an Always On availability group in SQL Server. This object is valid only on an instance of SQL Server that hosts a secondary replica.

Counter Name Description View on...
Database Flow Control Delay Duration spent in database flow control wait in microseconds. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Database Flow Controls/sec The number of database flow control per sec. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
File Bytes Received/sec Amount of FILESTREAM data received by the secondary replica for the secondary database in the last second. Secondary replica
Group Commit Time Number of microseconds all transactions group commit waited. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Group Commits/Sec Number of times transactions waited for group commit. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Log Apply Pending Queue Number of log blocks that are waiting to be applied to the database replica. Secondary replica
Log Apply Ready Queue Number of log blocks that are waiting and ready to be applied to the database replica. Secondary replica
Log Bytes Compressed/sec The amount of log in bytes compressed per sec. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Log Bytes Decompressed/sec The amount of log in bytes decompressed per sec. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Log Bytes Received/sec Amount of log records received by the secondary replica for the database in the last second. Secondary replica
Log Compression Cache hits/sec The number of log block compression hits per sec. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Log Compression Cache misses/sec The number of log block compression cache misses per sec. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Log Compressions/sec The number of log blocks compressed per sec. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Log Decompressions/sec The number of log blocks decompressed per sec. Applies to: SQL Server 2014 Service Pack 2 and later, SQL Server 2016 Service Pack 1 and later
Log remaining for undo The amount of log, in kilobytes, remaining to complete the undo phase. Secondary replica
Log Send Queue Amount of log records in the log files of the primary database, in kilobytes, that haven't been sent to the secondary replica. This value is sent to the secondary replica from the primary replica. Queue size doesn't include FILESTREAM files that are sent to a secondary. Secondary replica
Mirrored Write Transaction/sec Number of transactions that were written to the primary database and then waited to commit until the log was sent to the secondary database, in the last second. Primary replica
Recovery Queue Amount of log records in kilobytes in the log files of the secondary replica that have not been redone. Secondary replica
Redo blocked/sec Number of times the redo thread was blocked on locks held by readers of the database. Secondary replica
Redo Bytes Remaining The amount of log, in kilobytes, remaining to be redone to finish the reverting phase. Secondary replica
Redone Bytes/sec Amount of log records redone on the secondary database in the last second. Secondary replica
Redones/sec Amount of log records redone in the last second to catch up the database replica Secondary replica
Total Log requiring undo Total kilobytes of log that must be undone. Secondary replica
Transaction Delay Total delay in waiting for unterminated commit acknowledgment for all the current transactions, in milliseconds. Divide by Mirrored Write Transaction/sec to get Avg Transaction Delay. For more information, see Monitor performance for Always On availability groups Primary replica

Example

You begin to explore the query performance counters in this object using this T-SQL query on the sys.dm_os_performance_counters dynamic management view:

SELECT * FROM sys.dm_os_performance_counters
WHERE object_name LIKE '%Database Replica%';

See also

Monitor Resource Usage (System Monitor)
SQL Server, Availability Replica
SQL Server, Databases Object
Always On Availability Groups (SQL Server)