sys.dm_xtp_system_memory_consumers (Transact-SQL)

APPLIES TO: yesSQL Server yesAzure SQL Database noAzure Synapse Analytics (SQL DW) noParallel Data Warehouse

Reports system level memory consumers for In-Memory OLTP. The memory for these consumers comes either from the default pool (when the allocation is in the context of a user thread) or from internal pool (if the allocation is in the context of a system thread).

-- system memory consumers @ instance  
select * from sys.dm_xtp_system_memory_consumers  

For more information, see In-Memory OLTP (In-Memory Optimization).

Column name Type Description
memory_consumer_id bigint Internal ID for memory consumer.
memory_consumer_type int An integer that represents the type of the memory consumer with one of the following values:

0 - It should not be displayed. Aggregates memory usage of two or more consumers.

1 - LOOKASIDE: Tracks memory consumption for a system lookaside.

2 - VARHEAP: Tracks memory consumption for a variable-length heap.

4 - IO page pool: Tracks memory consumption for a system page pool used for IO operations.
memory_consumer_type_desc nvarchar(16) The description of the type of memory consumer:

0 - It should not be displayed.



memory_consumer_desc nvarchar(64) Description of the memory consumer instance:

System heap. General purpose. Currently only used to allocate garbage collection work items.
Lookaside heap. Used by looksides when the number of items contained in the lookaside list reaches a predetermined cap (usually around 5,000 items).

PGPOOL: For IO system pools there are three different sizes: System 4K page pool, System 64 K page pool, and System 256 K page pool.
lookaside_id bigint The ID of the thread-local, lookaside memory provider.
pagepool_id bigint The ID of the thread-local, page pool memory provider.
allocated_bytes bigint Number of bytes reserved for this consumer.
used_bytes bigint Bytes used by this consumer. Applies only to varheap memory consumers.
allocation_count int Number of allocations.
partition_count int Internal use only.
sizeclass_count int Internal use only.
min_sizeclass int Internal use only.
max_sizeclass int Internal use only.
memory_consumer_address varbinary Internal address of the consumer.


Requires VIEW SERVER STATE permissions on the server.

User Scenario

-- system memory consumers @ instance  
allocated_bytes/1024 as allocated_bytes_kb,   
used_bytes/1024 as used_bytes_kb, allocation_count  
from sys.dm_xtp_system_memory_consumers  

The output shows all memory consumers at system level. For example, there are consumers for transaction look aside.

memory_consumer_type_name           memory_consumer_desc                           allocated_bytes_kb   used_bytes_kb        allocation_count  
-------------------------------          ---------------------                          -------------------  --------------        ----------------  
VARHEAP                                  Lookaside heap                                 0                    0                    0  
VARHEAP                                  System heap                                    768                  0                    2  
LOOKASIDE                                GC transaction map entry                       64                   64                   910  
LOOKASIDE                                Redo transaction map entry                     128                  128                  1260  
LOOKASIDE                                Recovery table cache entry                     448                  448                  8192  
LOOKASIDE                                Transaction recent rows                        3264                 3264                 4444  
LOOKASIDE                                Range cursor                                   0                    0                    0  
LOOKASIDE                                Hash cursor                                    3200                 3200                 11070  
LOOKASIDE                                Transaction save-point set entry               0                    0                    0  
LOOKASIDE                                Transaction partially-inserted rows set        704                  704                  1287  
LOOKASIDE                                Transaction constraint set                     576                  576                  1940  
LOOKASIDE                                Transaction save-point set                     0                    0                    0  
LOOKASIDE                                Transaction write set                          704                  704                  672  
LOOKASIDE                                Transaction scan set                           320                  320                  156  
LOOKASIDE                                Transaction read set                           704                  704                  343  
LOOKASIDE                                Transaction                                    4288                 4288                 1459  
PGPOOL                                   System 256K page pool                          5120                 5120                 20  
PGPOOL                                   System 64K page pool                           0                    0                    0  
PGPOOL                                   System 4K page pool                            24                   24                   6  

To see the total memory consumed by system allocators:

select sum(allocated_bytes)/(1024*1024) as total_allocated_MB, sum(used_bytes)/(1024*1024) as total_used_MB   
from sys.dm_xtp_system_memory_consumers  
total_allocated_MB   total_used_MB  
-------------------- --------------------  
2                    2  

See Also

Memory-Optimized Table Dynamic Management Views (Transact-SQL)