System tenants

The system tenant is a built-in tenant of OceanBase Database.

The system tenant has the following characteristics:

• The system tenant manages all tenants and stores the metadata of all tenants. For example, the system tenant stores object metadata and location information about all system tables for user tenants.

• The system tenant executes centralized policies in a distributed cluster. For example, only the system tenant can perform rotating compaction, delete or create user tenants, modify system configurations, balance loads on resources, and enable automatic disaster recovery.

• The system tenant manages and maintains cluster resources. For example, the system tenant stores the information about all OBServers and zones in the cluster.

The system tenant is created when a bootstrap action is performed on the cluster. RootService manages the information and resources of the system tenant. RootService is a set of services that are enabled on the leader of the __all_core_table table for the system tenant. The __all_core_table table is table 1 of the system tenant. All other tables of the system tenant can be indexed by using table 1.

Classification of system tables

The system tenant is a MySQL-compatible tenant. System tables of the system tenant are classified into the following types:

• Object metadata tables

  The system tenant stores the metadata of all system tables. For example, the __all_core_table table stores the metadata of the __all_table_v2 table, and the __all_table_v2 table stores the metadata of other system tables.

• Tables used to store partition location information

  The system tenant stores the location information about system tables. For example, the __all_core_table table stores the location information about the __all_root_table table, and the __all_root_table table stores the location information about other system tables.

• Tables related to cluster resources

  The system tenant manages the location information and distribution information about all OBServers. For example, the __all_zone table stores the information about all zones, and the __all_server table stores the information about all OBServers.

• Tables related to tenant metadata and resources

  You can view the metadata of all tenants by using the system tenant. For example, the __all_tenant table stores the distribution information about all tenants in the cluster.

RootService

RootService provides the following features: cluster bootstrap, cluster resource management, DDL operations, and the execution of centralized policies in distributed clusters.

The following content describes the features of RootService:

• Cluster bootstrap

  You can configure a cluster bootstrap action to create the system tenant and initialize the configurations after an OBServer starts.

  You must specify the location of RootService for system bootstrap. The bootstrap command creates the __all_core_table table at the location of RootService. The OBServer in which the leader of the __all_core_table table resides automatically provides RootService. After you start RootService, you can create the system tenant and system tables, initialize system data, and configure the cluster.

• Cluster resource management

  Cluster resource management includes the following items:

  • Zone management

    You can add, delete, modify, and stop zones in the system tenant.

  • Resource unit management

    A resource unit is a minimum unit that is used to divide resources. A set of resource units constitute a resource pool, which can be allocated to a tenant. One tenant can have multiple resource pools. In the system tenant, you can adjust the resource unit specifications to adjust the resource pool size. This way, the tenant resources are adjusted.

    For more information, see Vertical scaling of tenant resources.

• OBServer management

  Each OBServer communicates with RootService by using heartbeats. RootService detects whether an OBServer is online and available based on its heartbeat information. You can add, delete, and stop OBServers in the system tenant.

• DDL operations

  All DDL operations are performed on RootService.

• Execution of centralized policies in distributed systems

  This feature involves the following aspects:

  • Role switchover of primary/standby cluster

    OceanBase clusters are deployed in primary/standby mode, including one primary cluster and multiple standby clusters. You can perform lossless or lossy switchover between clusters in the system tenant.

  • Major compaction management

    The system tenant manages the major compaction information about each version. RootService performs major compaction scheduling based on the information.

  • Configuration modification

    You can modify cluster-specific parameters such as enable_rebalance and enable_rereplication only in the system tenant.

  • Tenant management

    You can add, modify, and delete user tenants in the system tenant.

Advanced features

The system tenant provides the following advanced features:

• Global virtual tables

  The system tenant is a MySQL-compatible tenant, and the related views are compatible with MySQL. Specific global views exist in the system tenant. For example, the __all_virtual_meta_table table stores the content of the __all_tenant_meta_table table of all tenants, and the __all_virtual_ddl_operation table stores the content of the __all_ddl_operation table of all tenants.

• ALTER SYSTEM command

  You can run the ALTER SYSTEM command to perform cluster-specific operations, such as switching between primary and standby clusters and modifying configurations.