Azure SQL glossary of terms
Applies to: 
Azure SQL Database
Azure SQL Managed Instance
SQL Server on Azure VM
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Azure SQL Database
| Context | Term | Definition |
|---|---|---|
| Azure service | Azure SQL Database | Azure SQL Database is a fully managed platform as a service (PaaS) database that handles most database management functions such as upgrading, patching, backups, and monitoring without user involvement. |
| Database engine | The database engine used in Azure SQL Database is the most recent stable version of the same database engine shipped as the Microsoft SQL Server product. Some database engine features are exclusive to Azure SQL Database or are available before they are shipped with SQL Server. The database engine is configured and optimized for use in the cloud. In addition to core database functionality, Azure SQL Database provides cloud-native capabilities such as Hyperscale and serverless compute. | |
| Server entity | Logical server | A logical server is a construct that acts as a central administrative point for a collection of databases in Azure SQL Database and Azure Synapse Analytics. All databases managed by a server are created in the same region as the server. A server is a purely logical concept: a logical server is not a machine running an instance of the database engine. There is no instance-level access or instance features for a server. |
| Deployment option | Databases can be deployed individually or as part of an elastic pool. You can move existing databases in and out of elastic pools. | |
| Elastic pool | Elastic pools are a simple, cost-effective solution for managing and scaling multiple databases that have varying and unpredictable usage demands. The databases in an elastic pool are on a single logical server. The databases share a set allocation of resources at a set price. | |
| Single database | If you deploy single databases, each database is isolated, using a dedicated database engine. Each has its own service tier within your selected purchasing model and a compute size defining the resources allocated to the database engine. | |
| Purchasing model | Azure SQL Database has two purchasing models. The purchasing model defines how you scale your database and how you are billed for compute, storage, etc. | |
| DTU-based purchasing model | The Database Transaction Unit (DTU)-based purchasing model is based on a bundled measure of compute, storage, and I/O resources. Compute sizes are expressed in DTUs for single databases and in elastic database transaction units (eDTUs) for elastic pools. | |
| vCore-based purchasing model (recommended) | A virtual core (vCore) represents a logical CPU. The vCore-based purchasing model offers greater control over the hardware configuration to better match compute and memory requirements of the workload, pricing discounts for Azure Hybrid Benefit (AHB) and Reserved Instance (RI), more granular scaling, and greater transparency in hardware details. Newer capabilities (for example, Hyperscale, serverless) are only available in the vCore model. | |
| Service tier | The service tier defines the storage architecture, storage and I/O limits, and business continuity options. Options for service tiers vary by purchasing model. | |
| DTU-based service tiers | Basic, Standard, and Premium service tiers are available in the DTU-based purchasing model. | |
| vCore-based service tiers (recommended) | General Purpose, Business Critical, and Hyperscale service tiers are available in the vCore-based purchasing model (recommended). | |
| Compute tier | The compute tier determines whether resources are continuously available (provisioned) or autoscaled (serverless). Compute tier availability varies by purchasing model and service tier. Only the vCore purchasing model's General Purpose service tier makes serverless compute available. | |
| Provisioned compute | The provisioned compute tier provides a specific amount of compute resources that are continuously provisioned independent of workload activity. Under the provisioned compute tier, you are billed at a fixed price per hour. | |
| Serverless compute | The serverless compute tier autoscales compute resources based on workload activity and bills for the amount of compute used per second. Azure SQL Database serverless is currently available in the vCore purchasing model's General Purpose service tier with standard-series (Gen5) hardware or newer. | |
| Hardware configuration | Available hardware configurations | The vCore-based purchasing model allows you to select the appropriate hardware configuration for your workload. Hardware configuration options include standard series (Gen5), Fsv2-series, and DC-series. |
| Compute size (service objective) | Compute size (service objective) is the amount of CPU, memory, and storage resources available for a single database or elastic pool. Compute size also defines resource consumption limits, such as maximum IOPS, maximum log rate, etc. | |
| vCore-based sizing options | Configure the compute size for your database or elastic pool by selecting the appropriate service tier, compute tier, and hardware for your workload. When using an elastic pool, configure the reserved vCores for the pool, and optionally configure per-database settings. For sizing options and resource limits in the vCore-based purchasing model, see vCore single databases, and vCore elastic pools. | |
| DTU-based sizing options | Configure the compute size for your database or elastic pool by selecting the appropriate service tier and selecting the maximum data size and number of DTUs. When using an elastic pool, configure the reserved eDTUs for the pool, and optionally configure per-database settings. For sizing options and resource limits in the DTU-based purchasing model, see DTU single databases and DTU elastic pools. |
Azure SQL Managed Instance
| Context | Term | More information |
|---|---|---|
| Azure service | Azure SQL Managed Instance | Azure SQL Managed Instance is a fully managed platform as a service (PaaS) deployment option of Azure SQL. It gives you an instance of SQL Server, including the SQL Server Agent, but removes much of the overhead of managing a virtual machine. Most of the features available in SQL Server are available in SQL Managed Instance. Compare the features in Azure SQL Database and Azure SQL Managed Instance. |
| Database engine | The database engine used in Azure SQL Managed Instance has near 100% compatibility with the latest SQL Server (Enterprise Edition) database engine. Some database engine features are exclusive to managed instances or are available in managed instances before they are shipped with SQL Server. Managed instances provide cloud-native capabilities and integrations such as a native virtual network (VNet) implementation, automatic patching and version updates, automated backups, and high availability. | |
| Server entity | Managed instance | Each managed instance is itself an instance of SQL Server. Databases created on a managed instance are colocated with one another, and you can run cross-database queries. You can connect to the managed instance and use instance-level features such as linked servers and the SQL Server Agent. |
| Deployment option | Managed instances can be deployed individually or as part of an instance pools (preview). Managed instances cannot currently be moved into, between, or out of instance pools. | |
| Single instance | A single managed instance is deployed to a dedicated set of isolated virtual machines that run inside the customer's virtual network subnet. These machines form a virtual cluster. Multiple managed instances can be deployed into a single virtual cluster if desired. | |
| Instance pool (preview) | Instance pools enable you to deploy multiple managed instances to the same virtual machine. Instance pools enable you to migrate smaller and less compute-intensive workloads to the cloud without consolidating them in a single larger managed instance. | |
| Purchasing model | vCore-based purchasing model | SQL Managed Instance is available under the vCore-based purchasing model. Azure Hybrid Benefit is available for managed instances. |
| Service tier | vCore-based service tiers | SQL Managed Instance offers two service tiers that guarantee 99.99% availability and enable you to independently select storage size and compute capacity. Select from the General Purpose, or Business Critical service tier for a managed instance based upon your performance and latency requirements. |
| Compute | Provisioned compute | SQL Managed Instance provides a specific amount of compute resources that are continuously provisioned independent of workload activity, and bills for the amount of compute provisioned at a fixed price per hour. |
| Hardware configuration | Available hardware configurations | SQL Managed Instance hardware configurations include standard-series (Gen5), premium-series, and memory optimized premium-series hardware. |
| Compute size | vCore-based sizing options | Compute size (service objective) is the maximum amount of CPU, memory, and storage resources available for a single managed instance or instance pool. Configure the compute size for your managed instance by selecting the appropriate service tier and hardware for your workload. Learn about resource limits for managed instances. |
SQL Server on Azure VMs
| Context | Term | More information |
|---|---|---|
| Azure service | SQL Server on Azure Virtual Machines (VMs) | SQL Server on Azure VMs enables you to use full versions of SQL Server in the cloud without having to manage any on-premises hardware. SQL Server VMs simplify licensing costs when you pay as you go. You have both SQL Server and OS access with some automated manageability features for SQL Server VMs, such as the SQL Server IaaS Agent extension. |
| Server entity | Virtual machine or VM | Azure VMs run in many geographic regions around the world. They also offer various machine sizes. The virtual machine image gallery allows you to create a SQL Server VM with the right version, edition, and operating system. |
| Image | Windows VMs or Linux VMs | You can choose to deploy SQL Server VMs with Windows-based images or Linux-based images. Image selection specifies both the OS version and SQL Server edition for your SQL Server VM. |
| Pricing | Pricing for SQL Server on Azure VMs is based on SQL Server licensing, operating system (OS), and virtual machine cost. You can reduce costs by optimizing your VM size and shutting down your VM when possible. | |
| SQL Server licensing cost | Choose the appropriate free or paid SQL Server edition for your usage and requirements. For paid editions, you pay by usage (also known as pay as you go) or use Azure Hybrid Benefit. | |
| OS and virtual machine cost | OS and virtual machine cost is based upon factors including your choice of image, VM size, and storage configuration. | |
| VM configuration | You need to configure settings including security, storage, and high availability/disaster recovery for your SQL Server VM. The easiest way to configure a SQL Server VM is to use one of our Marketplace images, but you can also use this quick checklist for a series of best practices and guidelines to navigate these choices. | |
| VM size | VM size determines processing power, memory, and storage capacity. You can collect a performance baseline and/or use the SKU recommendation tool to help select the best VM size for your workload. | |
| Storage configuration | Your storage configuration options are determined by your selection of VM size and selection of storage settings including disk type, caching settings, and disk striping. Learn how to choose a VM size with enough storage scalability for your workload and a mixture of disks (usually in a storage pool) that meet the capacity and performance requirements of your business. | |
| Security considerations | You can enable Microsoft Defender for SQL, integrate Azure Key Vault, control access, and secure connections to your SQL Server VM. Learn security guidelines to establish secure access to SQL Server VMs. | |
| SQL IaaS Agent extension | The SQL IaaS Agent extension (SqlIaasExtension) runs on SQL Server VMs to automate management and administration tasks. There's no extra cost associated with the extension. | |
| Automated patching | Automated Patching establishes a maintenance window for a SQL Server VM when security updates will be automatically applied by the SQL IaaS Agent extension. There can be other mechanisms for applying Automatic Updates. If you configure automated patching using the SQL IaaS Agent extension you should ensure that there are no other conflicting update schedules. | |
| Automated backup | Automated Backup automatically configures Managed Backup to Microsoft Azure for all existing and new databases on a SQL Server VM running SQL Server 2016 or later Standard, Enterprise, or Developer editions. |