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Some diagnostic Always On Availability Groups information can be obtained from the SQL Server ring buffers, or the sys.dm_os_ring_buffers dynamic management view (DMV). The ring buffers are created during SQL Server startup, and record alerts within the SQL Server system for internal diagnostics. They are not supported, but you can still extract valuable information from them when troubleshooting issues. These ring buffers provide another source of diagnostics when SQL Server hangs or has crashed.
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The following Transact-SQL (T-SQL) query retrieves all event records from the availability groups ring buffers.
To make the data more manageable, filter the data by date and the ring buffer type. The following query retrieves records from the specified ring buffer that occurred today.
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```sql
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DECLARE @runtime datetime
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SET @runtime = GETDATE()
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SELECTCONVERT (varchar(30), @runtime, 121) as data_collection_runtime,
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DATEADD (ms, -1* (inf.ms_ticks- ring.[timestamp]), GETDATE()) AS ring_buffer_record_time,
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ring.[timestamp] AS record_timestamp, inf.ms_ticksAS cur_timestamp, ring.*
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FROMsys.dm_os_ring_buffers ring
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CROSS JOINsys.dm_os_sys_info inf where ring_buffer_type='<RING_BUFFER_TYPE>'
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```
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The Record column in each record contains diagnostic data in XML format. The XML data differs between the ring buffer types. For more information on each ring buffer type, see [Availability groups ring buffer types](#BKMK_RingBufferTypes). To make the XML data more readable, you need to customize your T-SQL query to extract the desired XML elements. For example, the following query retrieves all events from the RING_BUFFER_HADRDBMGR_API ring buffer and formats the XML data into separate table columns.
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```sql
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WITH hadr(ts, type, record) AS
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(
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SELECTtimestampAS ts, ring_buffer_type AS type, CAST(record AS XML) AS record
record.value('(./Record/@id)[1]','bigint') AS [Record ID],
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record.value('(./Record/@time)[1]','bigint') AS [Time],
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record.value('(./Record/HadrDbMgrAPI/dbId)[1]', 'bigint') AS [DBID],
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record.value('(/Record/HadrDbMgrAPI/API)[1]', 'varchar(50)') AS [API],
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record.value('(/Record/HadrDbMgrAPI/Action)[1]', 'varchar(50)') AS [Action],
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record.value('(/Record/HadrDbMgrAPI/role)[1]', 'int') AS [Role],
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record.value('(/Record/Stack)[1]', 'varchar(100)') AS [Call Stack]
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FROM hadr
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ORDER BYrecord.value('(./Record/@time)[1]','bigint') DESC
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GO
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```
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## <aname="BKMK_RingBufferTypes"></a> Availability groups ring buffer types
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There are four availability groups ring buffers in sys.dm_os_ring_buffers. The table below describes the ring buffer types and a sample of the content of the Record column for each ring buffer type.
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**RING_BUFFER_HADRDBMGR_API**
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Records state transitions that have taken place or are taking place. When looking at the state transitions pay close attention to the objectType values.
Records internal method or function calls made by Always On activity. It can show information such as suspend, resume, or role changes, including both the entry and exit points.
You can parse the Record field from the ring buffer you are inspecting by using [value() Method (xml Data Type)](~/t-sql/xml/value-method-xml-data-type.md) in your query. To use this method, you first need to [CAST](~/t-sql/functions/cast-and-convert-transact-sql.md) the record column in the ring buffer into XML. For example, the query below demonstrates how to parse RING_BUFFER_HADRDBMGR_API into readable format using this method.
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```sql
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WITH hadr(ts, type, record) AS
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(SELECTtimestampAS ts, ring_buffer_type AS type, CAST(record AS XML) AS record
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FROMsys.dm_os_ring_buffers
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WHERE ring_buffer_type ='RING_BUFFER_HADRDBMGR_API')
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SELECT ts,
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type,
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record.value('(./Record/@id)[1]','bigint') AS [Record id],
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record.value('(./Record/@time)[1]','bigint') AS [Time],
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record.value('(./Record/HadrDbMgrAPI/dbId)[1]', 'bigint') AS [dbid],
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record.value('(/Record/HadrDbMgrAPI/API)[1]', 'varchar(50)') AS [API],
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record.value('(/Record/HadrDbMgrAPI/Action)[1]', 'varchar(50)') AS [Action],
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record.value('(/Record/HadrDbMgrAPI/role)[1]', 'int') AS [Role],
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record.value('(/Record/Stack)[1]', 'varchar(100)') AS [Call Stack]
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FROM hadr
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ORDER BYrecord.value('(./Record/@time)[1]','bigint') DESC
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GO
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```
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Some diagnostic Always On availability group (AG) information can be obtained from the SQL Server ring buffers, or the `sys.dm_os_ring_buffers` dynamic management view (DMV). The ring buffers are created during SQL Server startup, and record alerts within the SQL Server system for internal diagnostics. They aren't supported, but you can still extract valuable information from them when troubleshooting issues. These ring buffers provide another source of diagnostics when SQL Server hangs or has crashed.
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The following Transact-SQL (T-SQL) query retrieves all event records from the AG ring buffers.
To make the data more manageable, filter the data by date and the ring buffer type. The following query retrieves records from the specified ring buffer that occurred today.
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```sql
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DECLARE @start_of_today DATETIME,
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@start_of_tomorrow DATETIME;
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SET @start_of_today = CAST(FLOOR(CAST(GETDATE() AS FLOAT)) AS DATETIME);
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SET @start_of_tomorrow = DATEADD(DAY, 1, @start_of_today);
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DECLARE @runtime DATETIME;
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SET @runtime = GETDATE();
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SELECTCONVERT(VARCHAR(30), @runtime, 121) AS data_collection_runtime,
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DATEADD(ms, -1* (inf.ms_ticks-ring.timestamp), GETDATE()) AS ring_buffer_record_time,
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ring.timestampAS record_timestamp,
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inf.ms_ticksAS cur_timestamp,
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ring.*
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FROMsys.dm_os_ring_buffers ring
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CROSS JOINsys.dm_os_sys_info inf
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WHERE ring_buffer_type ='<RING_BUFFER_TYPE>'
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AND DATEADD(ms, -1* (inf.ms_ticks-ring.timestamp), GETDATE()) >= @start_of_today
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AND DATEADD(ms, -1* (inf.ms_ticks-ring.timestamp), GETDATE()) < @start_of_tomorrow;
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GO
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```
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The `record` column in each record contains diagnostic data in XML format. The XML data differs between the ring buffer types. For more information on each ring buffer type, see [Availability group ring buffer types](#BKMK_RingBufferTypes). To make the XML data more readable, you need to customize your T-SQL query to extract the desired XML elements. For example, the following query retrieves all events from the RING_BUFFER_HADRDBMGR_API ring buffer and formats the XML data into separate table columns.
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```sql
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WITH hadr (ts, type, record)
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AS (
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SELECTtimestampAS ts,
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ring_buffer_type AS type,
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CAST(record AS XML) AS record
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FROMsys.dm_os_ring_buffers
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WHERE ring_buffer_type ='RING_BUFFER_HADRDBMGR_API'
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)
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SELECT ts,
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type,
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record.value('(./Record/@id)[1]', 'bigint') AS [Record ID],
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record.value('(./Record/@time)[1]', 'bigint') AS [Time],
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record.value('(./Record/HadrDbMgrAPI/dbId)[1]', 'bigint') AS [DBID],
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record.value('(/Record/HadrDbMgrAPI/API)[1]', 'varchar(50)') AS [API],
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record.value('(/Record/HadrDbMgrAPI/Action)[1]', 'varchar(50)') AS [Action],
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record.value('(/Record/HadrDbMgrAPI/role)[1]', 'int') AS [Role],
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record.value('(/Record/Stack)[1]', 'varchar(100)') AS [Call Stack]
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FROM hadr
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ORDER BYrecord.value('(./Record/@time)[1]', 'bigint') DESC;
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GO
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```
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## <aid="BKMK_RingBufferTypes"></a> Availability group ring buffer types
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There are four AG ring buffers in `sys.dm_os_ring_buffers`. The following section describes the ring buffer types and a sample of the content of the `record` column for each ring buffer type.
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#### RING_BUFFER_HADRDBMGR_API
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Records state transitions that have taken place or are taking place. When looking at the state transitions, pay close attention to the `objectType` values.
Records internal method or function calls made by AG activity. It can show information such as suspend, resume, or role changes, including both the entry and exit points.
You can parse the `Record` field from the ring buffer you are inspecting by using the [value() Method (xml Data Type)](../../../t-sql/xml/value-method-xml-data-type.md) in your query. To use this method, you first need to [CAST](../../../t-sql/functions/cast-and-convert-transact-sql.md) the record column in the ring buffer into XML. For example, the following query demonstrates how to parse `RING_BUFFER_HADRDBMGR_API` into readable format using this method.
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```sql
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WITH hadr (ts, type, record)
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AS (
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SELECTtimestampAS ts,
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ring_buffer_type AS type,
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CAST(record AS XML) AS record
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FROMsys.dm_os_ring_buffers
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WHERE ring_buffer_type ='RING_BUFFER_HADRDBMGR_API'
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)
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SELECT ts,
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type,
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record.value('(./Record/@id)[1]', 'bigint') AS [Record id],
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record.value('(./Record/@time)[1]', 'bigint') AS [Time],
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record.value('(./Record/HadrDbMgrAPI/dbId)[1]', 'bigint') AS [dbid],
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record.value('(/Record/HadrDbMgrAPI/API)[1]', 'varchar(50)') AS [API],
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record.value('(/Record/HadrDbMgrAPI/Action)[1]', 'varchar(50)') AS [Action],
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record.value('(/Record/HadrDbMgrAPI/role)[1]', 'int') AS [Role],
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record.value('(/Record/Stack)[1]', 'varchar(100)') AS [Call Stack]
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FROM hadr
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ORDER BYrecord.value('(./Record/@time)[1]', 'bigint') DESC;
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GO
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```
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## Next steps
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-[Configure Extended Events for availability groups](always-on-extended-events.md)
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-[Identify waits associated with availability groups](always-on-wait-types.md)
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-[Ring Buffer target code for extended events in Azure SQL Database](/azure/azure-sql/database/xevent-code-ring-buffer)
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