ApsaraDB RDS Glossary

AliSQL AliSQL is an independent MySQL branch developed by Alibaba Cloud. It includes all MySQL Community Edition features plus some similar enterprise-grade capabilities — such as backup and restoration, thread pools, and parallel queries — and Oracle-compatible features like the Sequence engine. ApsaraDB RDS for MySQL uses the AliSQL kernel and adds further enterprise features including enhanced security, monitoring, performance optimization, and read-only instances. For more information, see Overview of AliSQL features.

AliPG AliPG is the PostgreSQL-compatible database kernel developed by Alibaba Cloud. In commercial use since 2015, it is fully compatible with open source PostgreSQL and supports mainstream PostgreSQL versions. All PostgreSQL-compatible cloud database services in ApsaraDB RDS use AliPG. For more information, see AliPG benefits.

Asynchronous mode In asynchronous mode, the primary RDS instance responds to the application immediately after a write operation completes and replicates the data to secondary instances in parallel. Secondary instance unavailability does not interrupt workloads on the primary. However, if the primary fails, data inconsistencies between primary and secondary instances may occur.

Backup ApsaraDB RDS performs automatic backups on a regular schedule to protect data integrity and support restoration. For more information, see Overview, Back up an ApsaraDB RDS for SQL Server instance, Back up an ApsaraDB RDS for PostgreSQL instance, and Back up an ApsaraDB RDS for MariaDB instance.

Character set A character set is a collection of letters, symbols, and encoding rules used in a database.

Classic network The classic network is an Alibaba Cloud network type where instances cannot be isolated at the network level. Access is controlled exclusively through IP address whitelists or security groups. For stronger isolation and better performance, use a VPC instead.

Connections Connections are TCP connections between a database client and an RDS instance. When connection pooling is enabled on the client, connections are long-lived — they remain open after requests are processed rather than being closed after each request. For more information, see Configure the connection pooling feature.

CPU utilization CPU utilization is the resources consumed by programs and processes in the database system over a given period.

DAS Database Autonomy Service (DAS) is an Alibaba Cloud service that uses machine learning and expert knowledge to automate database perception, self-healing, optimization, operations and maintenance (O&M), and security. DAS reduces the risk of failures caused by manual operations and keeps databases running stably, securely, and efficiently. For more information, see Overview of DAS, Overview of DAS, and Overview of DAS.

Database A database is a logical unit within an RDS instance — an organized, minimal-redundancy collection of data that is independent of applications and can be shared among authorized users. You can create multiple databases on a single RDS instance; each database name must be unique within that instance.

Database proxy A database proxy sits between your application and the RDS instance cluster. It routes requests to the primary and read-only instances and provides high availability, high performance, and advanced features such as automatic read/write splitting, transaction splitting, and connection pooling. For more information, see What are database proxies?

Deadlock A deadlock occurs when two or more concurrent transactions each hold a lock on a resource that another transaction needs, preventing any of them from proceeding. Deadlocks are most common when multiple transactions attempt to modify the same set of resources.

Dedicated RDS instance A dedicated RDS instance has exclusive CPU and memory resources. Its performance is not affected by other instances on the same physical host. The highest tier — a dedicated host instance — occupies all resources of the physical host. For more information, see Instance families.

DMS Data Management (DMS) is a GUI-based database management tool developed by Alibaba Cloud. It supports data management, schema management, server management, access control, BI charting, data trend analysis, data tracking, and performance monitoring. DMS works with relational databases (MySQL, SQL Server, PostgreSQL, MongoDB, and Redis), NoSQL databases, and Linux-based database servers. For more information, see What is DMS?

DTS Data Transmission Service (DTS) is an Alibaba Cloud service for migrating, subscribing to, and synchronizing data between relational databases, NoSQL databases, and online analytical processing (OLAP) databases over stable, secure transmission links. For more information, see What is DTS?

ECS Elastic Compute Service (ECS) is a scalable, virtual machine-based compute service provided by Alibaba Cloud. It is commonly used alongside ApsaraDB RDS to build applications. For more information, see What is ECS?

Emergency RDS instance An emergency RDS instance is a temporary sandbox instance created by the Data Disaster Recovery service's sandbox feature, which is based on copy data management (CDM). It makes backup data available quickly for emergency recovery, without affecting data in other sandbox instances or the source database. Use cases include disaster recovery drills, development and testing, data queries, and emergency recovery. For more information, see Use the emergency recovery feature for an ApsaraDB RDS for MySQL instance.

ESSD An Enhanced SSD (ESSD) is a cloud disk type in ApsaraDB RDS built on a next-generation distributed block storage architecture. ESSDs integrate 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies, deliver low one-way latency, and support up to 1,000,000 random read/write operations per second. ESSDs come in three performance levels: For more information, see Storage types.

Full data migration Full data migration is a DTS operation that copies all objects from the source RDS instance to a destination instance at a point in time.

I/O Read and write operations performed on a disk.

IOPS Input/output operations per second (IOPS) is the number of 4 KB read or write operations a block storage device can process per second.

Incremental data migration After full data migration completes, DTS synchronizes ongoing data changes from the source to the destination RDS instance, keeping both in sync and allowing services to continue running during migration.

IP address whitelist An IP address whitelist defines the IP addresses and CIDR blocks allowed to connect to an RDS instance. Update whitelists regularly as your network environment changes. For more information, see Configure an IP address whitelist, Configure an IP address whitelist, Configure an IP address whitelist, and Configure an IP address whitelist.

JDBC Java Database Connectivity (JDBC) is a Java API for connecting to a database from a client application.

Local disk Local disks are local SSDs co-located on the same physical host as the RDS instance. Storing data on local disks reduces I/O latency compared to network-attached cloud disks. For more information, see Storage types.

Logical I/O Read and write operations performed by an application on a file system.

MaxCompute MaxCompute (formerly ODPS) is a fully managed big data computing platform that processes terabytes to petabytes of data at high speed. It supports bulk data import from RDS instances for large-scale analysis. For more information, see What is MaxCompute?

Microsoft AD Microsoft Active Directory (AD) is a directory service used across the Windows ecosystem for centralized identity and access management. ApsaraDB RDS for SQL Server and RDS for PostgreSQL support joining a self-managed AD domain. For more information, see Connect an ApsaraDB RDS for SQL Server instance to a self-managed domain and Connect an ApsaraDB RDS for PostgreSQL instance to a self-managed AD domain.

MongoDB ApsaraDB for MongoDB is a stable, reliable, and scalable database service fully compatible with the MongoDB protocol. Use ApsaraDB RDS for structured relational data and ApsaraDB for MongoDB for unstructured data. For more information, see What is ApsaraDB for MongoDB?

OSS Object Storage Service (OSS) is a secure, cost-effective, and high-durability cloud storage service from Alibaba Cloud for storing large volumes of data. For more information, see What is OSS?

OpenAPI ApsaraDB RDS provides an API for third-party developers. For more information, see List of operations by function.

Pay-as-you-go Pay-as-you-go instances are billed hourly based on actual resource usage. This billing method suits short-term or unpredictable workloads. Release instances when they are no longer needed to stop incurring charges. For long-term, predictable workloads, subscription billing is more cost-effective. For a comparison with subscription billing, see Billable items.

Performance Insight Performance Insight is a DAS feature that provides instance-level load monitoring, association analysis, and performance optimization recommendations. It helps you evaluate database load and troubleshoot performance bottlenecks.

Premium Local SSD Premium Local SSDs are high-performance local SSDs co-located on the same physical host as the RDS instance, providing low I/O latency. For more information, see Storage types.

QPS Queries per second (QPS) is the number of SQL statements — including INSERT, SELECT, UPDATE, DELETE, and COMMIT — executed on an RDS instance per second.

Random I/O Read and write operations that access non-sequential locations on a disk.

RAM Resource Access Management (RAM) is an Alibaba Cloud identity and access management service. Use RAM to grant fine-grained permissions on specific RDS instances to individual users or roles. For more information, see What is RAM?

RDS ApsaraDB RDS is a stable, reliable, and scalable online database service built on the Apsara Distributed File System and high-performance SSDs. It supports MySQL, SQL Server, PostgreSQL, and MariaDB, and provides a complete suite of capabilities for disaster recovery, backup, restoration, monitoring, and migration. For more information, see What is ApsaraDB RDS?

RDS Basic Edition RDS Basic Edition is cost-effective. A database system in this edition consists of a single primary RDS instance with compute and storage separated. For more information, see RDS Basic Edition, RDS Basic Edition, and RDS Basic Edition.

RDS Cluster Edition RDS Cluster Edition is available for MySQL, SQL Server, and PostgreSQL with engine-specific architectures:

• MySQL: One primary node and multiple secondary nodes with compute-storage separation. Features include automated failover, primary/secondary switchover, readable secondary nodes, node addition and deletion, multi-zone disaster recovery, and cluster topology management. MySQL group replication (MGR) mode supports a recovery point objective (RPO) of 0. For more information, see RDS Cluster Edition.

• SQL Server: One primary node and one secondary node using the native Always On architecture with compute-storage separation. Supports up to seven read-only instances for read/write splitting. For more information, see RDS Cluster Edition.

• PostgreSQL: One primary node and multiple secondary nodes with compute-storage separation. Features include automated failover, primary/secondary switchover, readable secondary nodes, node addition and deletion, multi-zone disaster recovery, and cluster topology management. For more information, see RDS Cluster Edition.

RDS Enterprise Edition RDS Enterprise Edition is designed for enterprise workloads requiring strong data consistency. A database system in this edition consists of one primary instance, one secondary instance, and one logger instance. Data is replicated from primary to secondary and logger in synchronous mode, providing finance-grade reliability. For more information, see RDS Enterprise Edition.

RDS High-availability Edition In RDS High-availability Edition, a secondary instance serves as a standby for the primary. Data is replicated in semi-synchronous mode. If the primary fails, the database system automatically fails over to the secondary. For more information, see RDS High-availability Edition, RDS High-availability Edition, RDS High-availability Edition, and RDS High-availability Edition.

RDS instance An RDS instance is a database process with dedicated memory resources running on a physical host — essentially a virtual database server. Each instance can run multiple databases and is independently configurable with different memory sizes, storage capacities, and database engines.

Read-only RDS instance A read-only RDS instance offloads read requests from the primary instance, increasing the overall read throughput of your database system. Use read-only instances when your workload is read-heavy. For more information, see Overview of read-only ApsaraDB RDS for MySQL instances, Overview of read-only ApsaraDB RDS for SQL Server instances, and Overview of read-only ApsaraDB RDS for PostgreSQL instances.

Read-only QPS The number of SELECT statements executed per second when only read operations are performed on the database.

Read and write QPS The number of INSERT, SELECT, and UPDATE statements executed per second when both read and write operations are performed on the database.

Recycle bin Expired or manually released RDS instances are moved to the recycle bin, where you can unlock, rebuild, or permanently destroy them. For more information, see Use the recycle bin feature, Use the recycle bin feature, Use the recycle bin feature, and Use the recycle bin feature.

Region A region is the geographic location where your RDS instance resides. Specify the region when you create an instance — it cannot be changed afterward.

Schema migration Schema migration is a DTS operation that copies the schemas (table structures, indexes, and other objects) from the source instance to a destination instance, without copying data.

Semi-synchronous mode In semi-synchronous mode, a write transaction on the primary is considered committed only after at least one secondary instance acknowledges receiving the transaction log record (not after the log is replayed). If a secondary RDS instance is unavailable or a network interruption occurs, the mode automatically degrades to asynchronous mode.

Sequential I/O Read and write operations that access contiguous, ordered locations on a disk.

Service account The service account is a temporary account used by Alibaba Cloud technical support engineers to troubleshoot issues on your RDS instance. Granting access is required before engineers can perform operations. The account is automatically deleted when the authorization period ends. For more information, see Grant permissions to the service account of an ApsaraDB RDS for MySQL instance and Grant permissions to the service account of an ApsaraDB RDS for SQL Server instance.

Slow SQL statement A slow SQL statement is any SQL query that exceeds the configured execution time threshold. For more information, see Use the slow query log analysis feature.

SSL Secure Sockets Layer (SSL) is a protocol for establishing encrypted connections, originally developed by Netscape. The IETF later standardized it as TLS. ApsaraDB RDS supports SSL for MySQL, SQL Server, and PostgreSQL. Each RDS instance has a server SSL certificate you can use to verify that a connection reaches your instance rather than an intermediary — protecting against man-in-the-middle attacks. For more information, see SSL encryption, Configure the SSL encryption feature, and SSL encryption.

SSMS SQL Server Management Studio (SSMS) is an integrated environment for managing SQL Server infrastructure. Use it to configure, monitor, and manage SQL Server instances and generate queries and scripts for databases and data warehouses. For more information, see Connect to an ApsaraDB RDS for SQL Server instance.

Standard SSD A standard SSD is an elastic block storage device based on a distributed storage architecture. It is a cloud disk type in ApsaraDB RDS that separates compute from storage. For more information, see Storage types.

Subscription Subscription instances are billed with an upfront payment for a fixed period. This billing method is more cost-effective than pay-as-you-go for long-running, predictable workloads — longer subscription periods get lower per-unit prices. For a comparison with pay-as-you-go billing, see Billable items.

Synchronous mode In synchronous mode, a write transaction on the primary is considered committed only after at least one secondary instance acknowledges receiving the transaction log record. Unlike semi-synchronous mode, synchronous mode never degrades to asynchronous mode. This mode is available only in RDS Enterprise Edition and cannot be changed once configured.

Tair (Redis OSS-compatible) Tair (Redis OSS-compatible) is a hybrid memory and disk database service that ensures data persistence. Use it together with ECS and ApsaraDB RDS to handle high-volume read workloads with low latency. For more information, see What is Tair (Redis OSS-compatible)?

TDE Transparent data encryption (TDE) encrypts data files as they are written to disk and decrypts them when read into memory. ApsaraDB RDS supports TDE for MySQL, PostgreSQL, and SQL Server. Enabling TDE does not increase data file size or require any changes to your application configuration. For more information, see Configure TDE, Configure TDE, and Use the TDE feature.

TPM Transactions per minute (TPM) is the number of transactions executed on an RDS instance per minute.

TPS Transactions per second (TPS) is the number of transactions committed on an RDS instance per second.

VPC A Virtual Private Cloud (VPC) is an isolated, private network on Alibaba Cloud. VPCs provide stronger network-level isolation and better performance than the classic network. For more information, see What is a VPC?

Zone A zone is a physical location within a region with independent power supply and network infrastructure. All zones within a region offer equivalent services.