Constraints

The following tables list the constraints designed to ensure the stability and security of TaurusDB for PostgreSQL.

Specifications and Performance

**Table 1** Specifications
Item	Constraints
Storage space	Cloud SSD: 40 GB to 4,000 GB Extreme SSD: 40 GB to 4,000 GB
Maximum connections	It depends on the value of max_connections.
IOPS	Cloud SSD: a maximum of 50,000 Extreme SSD: a maximum of 128,000

Quotas

**Table 2** Quotas
Item	Constraints
Tags	A maximum of 20 tags can be added for a DB instance.
Free backup space	TaurusDB for PostgreSQL provides free backup space of the same size as your purchased storage space.
Retention period of automated backups	The default value is 7 days. The value ranges from 1 to 732 days.
Log query	Error log records: 2,000 Slow query log records: 2,000

Naming

**Table 3** Naming
Item	Constraints
Instance name	4 to 64 characters long Must start with a letter. Only letters (case sensitive), digits, hyphens (-), and underscores (_) are allowed.
Database name	1 to 63 characters long Only letters, digits, and underscores (_) are allowed. It cannot start with pg or a digit, and must be different from TaurusDB for PostgreSQL template database names. TaurusDB for PostgreSQL template databases include postgres, template0, and template1.
Account name	1 to 128 characters long Only letters, digits, hyphens (-), and underscores (_) are allowed. It must be different from system accounts. System accounts include rdsadmin, rdsuser, rdsbackup, and rdsmirror.
Backup name	4 to 64 characters long Must start with a letter. Only letters (case sensitive), digits, hyphens (-), and underscores (_) are allowed.
Parameter template name	1 to 64 characters long Only letters (case sensitive), digits, hyphens (-), underscores (_), and periods (.) are allowed.

Security

**Table 4** Security
Item	Constraints
root permissions	Only the root user is available on the instance creation page. TaurusDB for PostgreSQL supports root privilege escalation in specific scenarios. For details, see Privileges of the root User.
root password	8 to 32 characters long Must contain at least three types of the following characters: uppercase letters, lowercase letters, digits, and special characters (~!@#%^*-_=+?,).
Database port	2100 to 9500
Disk encryption	If you enable disk encryption during instance creation, the disk encryption status and the key cannot be changed later.
VPC	After a TaurusDB for PostgreSQL instance is created, the VPC cannot be changed.
Security group	By default, you can create a maximum of 100 security groups in your cloud account. By default, you can add up to 50 security group rules to a security group. One TaurusDB for PostgreSQL instance can be associated with one security group, and one security group can be associated with multiple TaurusDB for PostgreSQL instances.
System account	To provide O&M services, the system automatically creates system accounts when you create TaurusDB for PostgreSQL instances. These system accounts are unavailable to you. rdsAdmin: a management account with the highest permission. It is used to query and modify instance information, rectify faults, migrate data, and restore data. pg_execute_server_program: an account that allows executing programs on the database server as the user the database runs as with COPY and other functions which allow executing a server-side program. pg_read_all_settings: an account that reads all configuration variables. pg_read_all_stats: an account that reads all pg_stat_* views and uses various extension-related statistics. pg_stat_scan_tables: an account that executes monitoring functions that may take ACCESS SHARE locks on tables, potentially for a long time. pg_signal_backend: an account that signals another backend to cancel a query or terminate its session. pg_read_server_files: an account that allows reading files from any location the database can access on the server with COPY and other file-access functions. pg_write_server_files: an account that allows writing files to any location the database can access on the server with COPY and other file-access functions. pg_monitor: an account that reads and executes various monitoring views and functions. This role is a member of pg_read_all_settings, pg_read_all_stats, and pg_stat_scan_tables. rdsRepl: a replication account, used to synchronize data from the primary instance to the standby instance. rdsBackup: a backup account, used for backend backup. rdsMetric: a metric monitoring account used by watchdog to collect database status data.
Instance parameter	To ensure optimal performance of TaurusDB for PostgreSQL, you can modify parameters in the parameter template you created as needed.

Instance Operations

**Table 5** Instance operations
Item	Constraints
Instance deployment	ECSs where DB instances are deployed are not directly visible to you. You can only access the DB instances through IP addresses and database ports.
Data migration	You can migrate data from self-managed PostgreSQL databases, PostgreSQL databases built on other clouds, self-managed Oracle databases, RDS for MySQL, self-managed MySQL databases, or MySQL databases built on other clouds to TaurusDB for PostgreSQL, or from one TaurusDB for PostgreSQL instance to another. Data migration tools include Data Replication Service (DRS), pg_dump, and Data Admin Service (DAS). You are advised to use DRS because it is easy to use and can complete a migration task in minutes. DRS facilitates data transfer between databases, helping you reduce DBA labor costs and hardware costs.
Primary/Standby replication	TaurusDB for PostgreSQL uses a primary/standby dual-node replication cluster. You do not need to set up replication additionally. The standby DB instance is not visible to you and therefore you cannot access it directly.
High CPU usage	If the CPU usage is high or close to 100%, data read/write and database access will become slow, and an error will be reported during data deletion.
Rebooting a DB instance	TaurusDB for PostgreSQL instances cannot be rebooted through commands. They must be rebooted on the management console.
Stopping or starting a DB instance	You can temporarily stop pay-per-use instances to save money. After stopping your instance, you can restart it to begin using it again.
Viewing backups	You can download automated and manual backups for local storage. To download a backup, you can use OBS Browser+, the current browser, or the download URL.
Log management	TaurusDB for PostgreSQL logging is enabled by default and cannot be disabled.

Privileges of the root User

TaurusDB for PostgreSQL provides privileges for the root user. To create objects on a TaurusDB for PostgreSQL database without operation risks, escalate your account to root privileges when necessary.

The following table describes root privilege escalation in different versions.