Applies to: Azure SQL Database
This article provides the detailed resource limits for databases in Azure SQL Database that are within an elastic pool using the DTU purchasing model.
For each elastic pool, you can optionally specify per database minimum and maximum DTUs to modify resource consumption patterns within the pool. You can also set maximum storage per database, for example to prevent a single database from consuming all pool storage.
The following table describes per database properties for pooled databases.
Property Configuration level Description Max DTUs per database Configured for all databases in the pool The maximum number of DTUs that any database in the pool might use, if available based on utilization by other databases in the pool. Max DTUs per database is not a resource guarantee for a database. If the workload in each database does not need all available pool resources to perform adequately, consider setting max DTUs per database to prevent a single database from monopolizing pool resources. Some degree of over-committing is expected since the pool generally assumes hot and cold usage patterns for databases, where all databases are not simultaneously peaking. Min DTUs per database Configured for all databases in the pool The minimum number of DTUs reserved for any database in the pool. Consider setting a min DTUs per database when you want to guarantee resource availability for each database regardless of resource consumption by other databases in the pool. The min DTUs per database might be set to 0, and is also the default value. This property is set to anywhere between 0 and the average DTUs utilization per database. Max storage per database Configured per database The maximum database size set by the user for a database in a pool. Pooled databases share allocated pool storage, so the size a database can reach is limited to the smaller of remaining pool storage and maximum database size. Maximum database size refers to the maximum size of the data files and does not include the space used by the log file.Important
Because resources in an elastic pool are finite, setting min DTUs per database to a value greater than 0 implicitly limits resource utilization by each database. If, at a point in time, most databases in a pool are idle, resources reserved to satisfy the min DTUs guarantee are not available to databases active at that point in time.
Additionally, setting min DTUs per database to a value greater than 0 implicitly limits the number of databases that can be added to the pool. For example, if you set the min DTUs to 100 in a 400 DTU pool, it means that you will not be able to add more than 4 databases to the pool, because 100 DTUs are reserved for each database.
If all DTUs of an elastic pool are used, then each database in the pool receives an equal amount of resources to process queries. The Azure SQL Database service provides resource sharing fairness between databases by ensuring equal slices of compute time. Elastic pool resource sharing fairness is in addition to any amount of resource otherwise guaranteed to each database when the DTU min per database is set to a non-zero value.
While the per database properties are expressed in DTUs, they also govern consumption of other resource types, such as data IO, log IO, buffer pool memory, and worker threads. As you adjust min and max per database DTUs values, reservations and limits for all resource types are adjusted proportionally.
Min and max per database DTU values apply to resource consumption by user workloads, but not to resource consumption by internal processes. For example, for a database with a per database max DTU set to half of the pool eDTU, user workload cannot consume more than one half of the buffer pool memory. However, this database can still take advantage of pages in the buffer pool that were loaded by internal processes. For more information, see Resource consumption by user workloads and internal processes.
Each read-only replica has its own resources such as DTUs, workers, and sessions. Each read-only replica is subject to the resource limits detailed later in this article.
Tempdb sizesThe following table lists tempdb sizes for single databases in Azure SQL Database:
tempdb data file size (GB) Number of tempdb data files Maximum tempdb data size (GB) Basic Elastic Pools (all DTU configurations) 13.9 12 166.7 Standard Elastic Pools (50 eDTU) 13.9 12 166.7 Standard Elastic Pools (100 eDTU) 32 1 32 Standard Elastic Pools (200 eDTU) 32 2 64 Standard Elastic Pools (300 eDTU) 32 3 96 Standard Elastic Pools (400 eDTU) 32 3 96 Standard Elastic Pools (800 eDTU) 32 6 192 Standard Elastic Pools (1200 eDTU) 32 10 320 Standard Elastic Pools (1600-3000 eDTU) 32 12 384 Premium Elastic Pools (all DTU configurations) 13.9 12 166.7 Elastic pool: Storage sizes and compute sizes
For Azure SQL Database elastic pools, the following tables show the resources available at each service tier and compute size. You can set the service tier, compute size, and storage amount using:
The resource limits of individual databases in elastic pools are generally the same as for single databases outside of pools based on DTUs and the service tier. For example, the max concurrent workers for an S2 database is 120 workers. So, the max concurrent workers for a database in a Standard pool is also 120 workers if the max DTU per database in the pool is 50 DTUs (which is equivalent to S2).
For the same number of DTUs, resources provided to an elastic pool can exceed the resources provided to a single database outside of an elastic pool. This means it is possible for the eDTU utilization of an elastic pool to be less than the summation of DTU utilization across databases within the pool, depending on workload patterns. For example, in an extreme case with only one database in an elastic pool where database DTU utilization is 100%, it is possible for pool eDTU utilization to be 50% for certain workload patterns. This can happen even if max DTU per database remains at the maximum supported value for the given pool size.
Note
The storage per pool resource limit in each of the following tables do not include tempdb and log storage.
1 See Resource management in dense elastic pools for additional considerations.
2 For the max concurrent workers for any individual database, see Resource limits for single databases using the DTU purchasing model.
3 See External Connections for additional details on what counts as an external connection.
Standard elastic pool limits eDTUs per pool 50 100 200 300 400 800 Included storage per pool (GB) 1 50 100 200 300 400 800 Max storage per pool (GB) 500 750 1024 1280 1536 2048 Max In-Memory OLTP storage per pool (GB) N/A N/A N/A N/A N/A N/A Max number DBs per pool 2 100 200 500 500 500 500 Max concurrent workers per pool 3 100 200 400 600 800 1600 Max concurrent logins per pool 100 200 400 600 800 1600 Max concurrent external connections per pool 4 10 20 40 60 80 150 Max concurrent sessions per pool 3 30000 30000 30000 30000 30000 30000 Min DTU per database choices 0, 10, 20, 50 0, 10, 20, 50, 100 0, 10, 20, 50, 100, 200 0, 10, 20, 50, 100, 200, 300 0, 10, 20, 50, 100, 200, 300, 400 0, 10, 20, 50, 100, 200, 300, 400, 800 Max DTU per database choices 10, 20, 50 10, 20, 50, 100 10, 20, 50, 100, 200 10, 20, 50, 100, 200, 300 10, 20, 50, 100, 200, 300, 400 10, 20, 50, 100, 200, 300, 400, 800 Max storage per database (GB) 1024 1024 1024 1024 1024 10241 See SQL Database pricing options for details on additional cost incurred due to any extra storage provisioned.
2 See Resource management in dense elastic pools for additional considerations.
3 For the max concurrent workers for any individual database, see Resource limits for single databases using the DTU purchasing model.
4 See External Connections for additional details on what counts as an external connection.
Standard elastic pool limits (continued) eDTUs per pool 1200 1600 2000 2500 3000 Included storage per pool (GB) 1 1200 1600 2000 2500 3000 Max storage per pool (GB) 2560 3072 3584 4096 4096 Max In-Memory OLTP storage per pool (GB) N/A N/A N/A N/A N/A Max number DBs per pool 2 500 500 500 500 500 Max concurrent workers per pool 3 2400 3200 4000 5000 6000 Max concurrent logins per pool 2400 3200 4000 5000 6000 Max concurrent external connections per pool 4 150 150 150 150 150 Max concurrent sessions per pool 3 30000 30000 30000 30000 30000 Min DTU per database choices 0, 10, 20, 50, 100, 200, 300, 400, 800, 1200 0, 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600 0, 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600, 2000 0, 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600, 2000, 2500 0, 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600, 2000, 2500, 3000 Max DTU per database choices 10, 20, 50, 100, 200, 300, 400, 800, 1200 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600, 2000 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600, 2000, 2500 10, 20, 50, 100, 200, 300, 400, 800, 1200, 1600, 2000, 2500, 3000 Max storage per database (GB) 1024 1536 1792 2304 28161 See SQL Database pricing options for details on additional cost incurred due to any extra storage provisioned.
2 See Resource management in dense elastic pools for additional considerations.
3 For the max concurrent workers for any individual database, see Resource limits for single databases using the DTU purchasing model.
4 See External Connections for additional details on what counts as an external connection.
Premium elastic pool limits eDTUs per pool 125 250 500 1000 1500 Included storage per pool (GB) 1 250 500 750 1024 1536 Max storage per pool (GB) 1024 1024 1024 1024 1536 Max In-Memory OLTP storage per pool (GB) 1 2 4 10 12 Max number DBs per pool 2 50 100 100 100 100 Max concurrent workers per pool (requests) 3 200 400 800 1600 2400 Max concurrent logins per pool 200 400 800 1600 2400 Max concurrent external connections per pool 4 20 40 80 150 150 Max concurrent sessions per pool 3 30000 30000 30000 30000 30000 Min eDTUs per database 0, 25, 50, 75, 125 0, 25, 50, 75, 125, 250 0, 25, 50, 75, 125, 250, 500 0, 25, 50, 75, 125, 250, 500, 1000 0, 25, 50, 75, 125, 250, 500, 1000 Max eDTUs per database 25, 50, 75, 125 25, 50, 75, 125, 250 25, 50, 75, 125, 250, 500 25, 50, 75, 125, 250, 500, 1000 25, 50, 75, 125, 250, 500, 1000 Max storage per database (GB) 1024 1024 1024 1024 15361 See SQL Database pricing options for details on additional cost incurred due to any extra storage provisioned.
2 See Resource management in dense elastic pools for additional considerations.
3 For the max concurrent workers for any individual database, see Resource limits for single databases using the DTU purchasing model.
4 See External Connections for additional details on what counts as an external connection.
Premium elastic pool limits (continued) eDTUs per pool 2000 2500 3000 3500 4000 Included storage per pool (GB) 1 2048 2560 3072 3548 4096 Max storage per pool (GB) 2048 2560 3072 3548 4096 Max In-Memory OLTP storage per pool (GB) 16 20 24 28 32 Max number DBs per pool 2 100 100 100 100 100 Max concurrent workers per pool 3 3200 4000 4800 5600 6400 Max concurrent logins per pool 3200 4000 4800 5600 6400 Max concurrent external connections per pool 4 150 150 150 150 150 Max concurrent sessions per pool 3 30000 30000 30000 30000 30000 Min DTU per database choices 0, 25, 50, 75, 125, 250, 500, 1000, 1750 0, 25, 50, 75, 125, 250, 500, 1000, 1750 0, 25, 50, 75, 125, 250, 500, 1000, 1750 0, 25, 50, 75, 125, 250, 500, 1000, 1750 0, 25, 50, 75, 125, 250, 500, 1000, 1750, 4000 Max DTU per database choices 25, 50, 75, 125, 250, 500, 1000, 1750 25, 50, 75, 125, 250, 500, 1000, 1750 25, 50, 75, 125, 250, 500, 1000, 1750 25, 50, 75, 125, 250, 500, 1000, 1750 25, 50, 75, 125, 250, 500, 1000, 1750, 4000 Max storage per database (GB) 2048 2560 3072 3584 40961 See SQL Database pricing options for details on additional cost incurred due to any extra storage provisioned.
2 See Resource management in dense elastic pools for additional considerations.
3 For the max concurrent workers for any individual database, see Resource limits for single databases using the DTU purchasing model.
4 See External Connections for additional details on what counts as an external connection.
Important
More than 1 TB of storage in the Premium tier is currently available in all regions except: China East, China North, Germany Central, and Germany Northeast. In these regions, the storage max in the Premium tier is limited to 1 TB. For more information, see P11-P15 current limitations.
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