A-E

• A

  asynchronous replication

  After an application initiates a data update (including insert, delete, and modify data) request, Master commits data and returns a response to the application immediately. With asynchronous replication, Master does not need to wait for Slave and data is asynchronously replicated from Master to Slave. Therefore, the performance is high, but data may be inconsistent.

  automated backup

  RDS automatically creates full backups for DB instances. You can set the automated backup start time and backup retention period.

  availability priority

  During a primary/standby failover, if data is inconsistent between primary and standby DB instances and the synchronization delay is no more than 5 minutes, a failover is still performed to ensure service availability. If the delay is longer than five minutes, the failover is not performed and database services are stopped to prevent data loss.

• B

  backup retention period

  Retention period for automated backups. After the retention period expires, automated backups will be deleted automatically.

  backup storage

  The underlying storage resources used for storing backup data and logs of a database persistently.

• C

  cloud service provider

  A company or an organization that provides cloud computing services.

  cold backup

  A cold backup is performed when a system is stopped or being maintained. The backup data is completely the same as the data in the system at the point in time.

  CSP

  See cloud service provider

• D

  data replication

  In an HA architecture, data committed to a primary instance will be replicated to a standby instance. Data replications come in three types: fully synchronous replication, semi-synchronous replication, and asynchronous replication.

  database administrator

  A person who is responsible for managing databases. A DBA uses dedicated software to store and organize data. Their responsibilities include but are not limited to capacity planning, installation, configuration, database design, migration, performance monitoring, security, troubleshooting, and data backup and restoration.

  database administrator account

  A database administrator account is different from a user cloud account and used only within the RDS system to control access to RDS DB instances. You can use the database administrator account to access DB instances. For example, when you are creating a MySQL DB instance, the administrator account root is created by default and you can specify the root password. After the DB instance is created, you can connect to it using the root account. You can also create additional database accounts as needed.

  database migration

  As services develop, a database needs to be migrated from an environment to another, for example, from a local data center to a cloud, or from a cloud to another cloud.

  database storage

  The underlying storage resources used for storing data and logs of a database permanently.

  database type

  Database types are classified into relational databases and non-relational databases.

  DB connections

  The number of client sessions that are connected to a DB instance.

  DB engine

  A DB engine is vital for storing, processing, and protecting data. It can be used to control access permissions and process transactions rapidly. Each DB instance runs a DB engine.

  DB instance

  A DB instance is an isolated database environment in the cloud. It is a basic building block of RDS. A DB instance can contain multiple user-created databases. You can access your DB instance by using the same tools and applications that you use with a standalone DB instance.

  DB instance class

  The DB instance class determines the compute and memory capacity of a DB instance. You can change the CPU or memory of an available DB instance by changing its DB instance class.

  DB instance ID

  A DB instance ID uniquely identifies a DB instance in a region.

  DB instance lifecycle

  A DB instance lifecycle starts from the time when the DB instance is created to the time when the DB instance is deleted. During a DB instance lifecycle, you can back up and restore data, change instance classes, scale up storage space, and reboot or delete the instance.

  DB parameter template

  A database parameter template functions as a container for engine configuration values that can be applied to one or more DB instances. If you create a DB instance without specifying a parameter template, the default parameter template is used. Each default parameter template contains database engine defaults and RDS system defaults. You can also create your own parameter template where you choose your own parameter settings and apply the parameter template to DB instances. If you update parameters in a parameter template, the changes apply to all DB instances that are applied with the template.

  DBA

  See database administrator

F-J

• F

  failover****

  If an unexpected interruption occurs on a primary DB instance, RDS automatically switches to the standby DB instance to restore database operations quickly without manual intervention. The time required for completing a failover depends on the database activities and conditions when the primary DB instance became unavailable. The duration is usually from seconds to minutes. Large transactions or long restoration process may increase the failover duration.

  failover priority

  You can determine whether reliability or availability is given priority during a failover. By default, reliability is given priority.

  fully synchronous replication

  After an application initiates a data update (including insert, delete, and modify data) request, Master replicates the updated data to Slave and Slave writes the received data to relay logs and flushes it to disks. After Slave replays logs and commits transactions, it returns a successful message to Master. Master responds to the application only after receiving the message from Slave. Since data is synchronously replicated from Master to Slave, unavailability of Slave will affect operations on Master, and unavailability of Master will not cause data inconsistency.

• H

  HA

  See high availability

  high availability

  A system availability that keeps a service running properly without interruption.

  hot backup

  A hot backup is performed when a system is properly running. The backup data may be different from the actual data of the system because the data in the system keeps being updated.

• I

  incremental backup

  RDS automatically backs up data updated after the last automated or incremental backup every five minutes.

  input/output operations per second

  The number of I/O operations completed per second. This metric is reported as the average IOPS for a given time interval. RDS reports read and write IOPS separately at one minute intervals. Total IOPS is the sum of the read and write IOPS. Typical values for IOPS range from zero to tens of thousands per second.

  IOPS

  See input/output operations per second

K-O

• L

  license model

  License type associated with a DB engine.

  logical backup

  A procedure in which the structured query language (SQL) is used to abstract data from a database and store the data into a binary file. Logical backup is a technology that uses software to export data from a database and stores the data into a file which is in a format different from the file in the original database. Logical backup can only be used for logical restoration (data import) and cannot be used for physical restoration based on storage characters of the original database. Generally, logical backup is used for incremental backup and only backs up data that has changed since the last backup.

• M

  manual backup

  A user-initiated full backup of a DB instance. A manual backup is always retained until you explicitly delete it manually.

• N

  network traffic

  Network transmission throughput, indicating the rate of network traffic in and out of the DB instance in MB per second.

  non-relational database

  Data in a non-relational database is communicated and organized based on the non-relational data structure. Based on different data structures, non-relational databases can be classified as the following types: key-value, column-oriented, document-oriented, and graphic databases. Common non-relational databases include Memcached, Redis, MongoDB, Cassandra, HBase, MemcacheDB, and Berkeley DB.

P-T

• P

  performance metrics

  Metrics of DB instance performance, including the CPU usage, memory usage, storage space usage, network traffic, database connections, transaction rate/database throughput, submit latency, storage latency, storage IOPS, storage throughput, and storage queue length.

  physical backup

  A backup mechanism, in which database files in the operating system are replicated from one place to another place, generally from a disk to a tape. Physical backup includes cold backup and hot backup.

  primary DB instance

  A DB instance that provides read and write services.

• Q

  queue depth

  The number of I/O requests in the queue waiting to be serviced. These are I/O requests that have been submitted by the application but have not been sent to the device because the device is busy servicing other I/O requests. Time spent waiting in the queue is a component of Latency and Service Time (not available as a metric). This metric is reported as the average queue depth for a given time interval. RDS reports queue depth at one minute intervals. Typical values for queue depth range from zero to several hundred.

• R

  RDB

  See relational database

  RDS

  See Relational Database Service

  RDS DB instance

  An RDS DB instance is the minimum RDS management unit. An RDS DB instance represents a relational database that runs independently. You can create and manage DB instances of various database engines in the RDS system. RDS DB instances come in three types: primary DB instances, standby DB instances, and read replicas. RDS DB instances come in three types: primary DB instances, standby DB instances, and read replicas.

  read replica

  An active copy of a DB instance. Any updates to the data on the source DB instance are replicated to the read replicas using the built-in replication feature of the DB engine.

  read/write splitting

  Primary DB instances process INSERT, UPDATE, and DELETE requests and standby DB instances process SELECT requests.

  relational database**

  Tables in a relational database are communicated and organized based on the relational data structure. RDB simplifies complex data structures into simple binary relations (two-dimensional tables). A relational database contains multiple tables and each table is known as a relation. Data management is performed through data manipulation language (DML) statements, such as GROUP BY, JOIN, UNION, and SELECT * FROM. Common relational databases include Oracle, MySQL, MariaDB, Microsoft SQL Server, Access, DB2, PostgreSQL, Informix, and Sybase.

  Relational Database Service

  RDS is a managed service that makes it easy to create, configure, operate, and scale a relational database in the cloud.

  reliability priority

  During a primary/standby failover, if data is inconsistent between primary and standby DB instances, the failover is not performed and database services are stopped to ensure data consistency.

• S

  Secure Sockets Layer

  A security protocol that works at a socket layer. This layer exists between the TCP layer and the application layer to encrypt/decode data and authenticate concerned entities.

  semi-synchronous replication

  After an application initiates a data update (including insert, delete, and modify data) request, Master replicates the updated data to Slave. When at least one Slave receives binlogs, writes data to relay logs and flushes it to disks, Slave returns a response to Master. Compared to fully synchronous replication, semi-synchronous replication is faster because Master does not wait for Slave to commit data. However, since Slave responds to Master before the commitment is done, data may be inconsistent.

  solid-state drive

  SSDs are built on solid electronic storage chip arrays. Each SSD consists of a control unit and a storage unit (a flash and a DRAM chip). The interface specifications, definition, functions, and usage of an SSD are the same as those of a common hard disk. SSDs are widely applied in fields such as military, vehicles, industrial control, video surveillance, network surveillance, network terminals, electricity, medical, aeronautics, and navigation equipment.

  source DB instance

  A source DB instance functions as the data source in data replication.

  SSD

  See solid-state drive

  SSL

  See Secure Sockets Layer

  standby DB instance

  A standby DB instance is a backup for a primary DB instance. If the primary instance fails, the standby instance automatically takes over services to improve database availability.When creating a primary DB instance, you can determine whether to create a synchronous standby DB instance with the same specifications as the primary one.

  storage space

  The space of underlying storage resources for storing data and logs of a database.

  storage type

  Storage can be classified as different types based on the dimensions and attributes of storage resources. For example, storage can be classified into magnetic storage and SSD based on storage media, and can be classified into general, medium, and high performance I/O based on the I/O level.

  submit latency

  The elapsed time between the submission of a request and its completion. This metric is closely related with the storage write latency metric. A high storage write latency may cause a high submit latency.

• T

  throughput

  The number of bytes per second transferred to or from a disk. An average throughput is reported at a specified interval. RDS reports read and write throughput in MB/s separately every one minute. Typical values for throughput are from zero to the I/O channel's maximum bandwidth.

  transaction rate/database throughput

  Number of completed transactions in a specified period, generally expressed in transactions per minute (TPM) or transactions per second (TPS). Another term for transaction rate is database throughput. Do not confuse it with the disk throughput. Databases have high transaction rates, so there is little or no disk throughput.

U-Z

• U

  unsynchronized data

  For primary/standby MySQL or PostgreSQL DB instances, when the failover priority is given to availability, the primary DB instance may have more data than the standby instance due to synchronization delay or other reasons. After a failover occurs, the primary DB instance is demoted to be standby and the standby DB instance is promoted to be primary. The data that has not been synchronized to the new primary DB instance (original standby) will be packaged and uploaded to OBS in SQL statements for download.