OceanBase Database adopts a multi-tenant architecture. This architecture is suitable for resource consolidation, cloud services and other scenarios, and also reduces operational complexity.
As of OceanBase Database v4.0, there are three types of tenants: system tenant, user tenant, and meta tenant corresponding to each user tenant.
Log on to a system tenant
The system tenant is a database instance used internally by the OceanBase Database to handle cluster-wide public tasks. The Root Service is based on the system tenant to undertake the management work of the OceanBase Database, including cluster management, tenant management, resource management, load balancing, scheduling of daily compaction tasks, and data migration and replication. The system tenant is the default tenant created for the cluster and is responsible for managing the lifecycle of the cluster and all tenants.
The system tenant is compatible with MySQL mode and can be accessed through both the MySQL client and OceanBase client (OBClient).
Log on through the MySQL client
The database connection string for logging in through the MySQL client is shown as follows:
mysql -h host IP address -P port number -u account name -p 'password' -D default database -Ac --prompt "OceanBase(\u@\d)> "
The main parameters are described as follows:
-h: host IP address for logging in to the OceanBase Database. You can log in either through the ODP or through a direct connection to an OBServer node. It is recommended to log in through the ODP as it makes optimal use of OceanBase's distributed features, including routing and disaster recovery.-P: port number for logging in to the OceanBase Database. You can change the port number in the configuration file during deployment. You can view themysql_portparameter of each OBServer node and thelisten_portparameter of the ODP in the configuration file. If no values are explicitly specified for these parameters, the default values are used.If you log in through the ODP, the default port number is 2883.
If you log in through a direct connection to an OBServer node, the default port number is 2881.
-u: account for logging in to the OceanBase Database. Unlike conventional databases, the account for the OceanBase Database contains more fields, including username, tenant name, and cluster name.If you log in through the ODP, you must specify the username, tenant name, and cluster name in the
username@tenant name#cluster nameformat. For example, if you want to log on as the root user to thesystenant of thetestcluster, your account name isroot@sys#test.If you log in through a direct connection to an OBServer node, you must specify the username and tenant name in the
username@tenant nameformat. For example,if you want to log on as the root user to thesystenant of thetestcluster, your account name isroot@sys.
-p: password for logging in to the OceanBase Database. For a new cluster, the initial password for the root user of thesystenant is empty. It is recommended to change the root user password usingalter user root identified by '******'as the first step after creating a new cluster.
For details about connecting to the OceanBase Database through the MySQL client, see Connect to an OceanBase Database tenant by using a MySQL client.
Log on through the OBClient
OBClient is a recommended CLI client tool for logging in to the OceanBase Database. You can use your OBClient account in a MySQL client. The database connection string for logging in through the OBClient is shown as follows:
obclient -h host IP address -P port number -u account name -p 'password' -D default database -Ac --prompt "OceanBase(\u@\d)> "
For details about connecting to the OceanBase Database through the OBClient, see Connect to an OceanBase Database tenant by using OBClient).
Best practices for logon
The root user has a high level of permissions and the abuse of the root user will pose a great security risk to the database. It is recommended that the root user only be used to manage other users and create dedicated O&M users and read-only users with the least permissions.
It is recommended that dedicated read-only users query views.
As of OceanBase Database v4.0, internal information is queried only in the form of views. The
systenant can query various views.obclient> use oceanbase obclient> show tables; +-------------------------------------------+ | Tables_in_oceanbase | +-------------------------------------------+ | CDB_INDEXES | | CDB_IND_COLUMNS | | CDB_IND_PARTITIONS | | CDB_IND_SUBPARTITIONS | | CDB_OBJECTS | | CDB_OB_ARCHIVELOG | | CDB_OB_ARCHIVELOG_PIECE_FILES | ...These views can be classified into two categories: data dictionary views and dynamic performance views.
Data dictionary views: The name of a data dictionary view begins with
DBA_orCDB_. A view whose name begins withDBA_displays the internal information of a tenant. For example, theDBA_OB_LSview displays information about log streams in the tenant; theDBA_OB_LSview in thesystenant displays only information about log streams in thesystenant itself.A view whose name begins with
CDB_is used for thesystenant. From thesystenant, you can query these views for the status of all tenants in the cluster. For example, theCDB_OB_LSview displays information about all log streams of all tenants in the cluster. Generally, for eachDBA_view, there is a correspondingCDB_view in thesystenant.Dynamic performance views: The name of a dynamic performance view begins with
GV$orV$. A view whose name begins withV$displays only information about the server to which you have logged on, and a view whose name begins withGV$displays information about all servers in the tenant. In OceanBase 4.0, many dynamic performance views have been added to a user tenant. For example, theGV$OB_UNITSview can be used to query information about the distribution of units within the tenant. The dynamic performance view of thesystenant displays information about all tenants in the cluster.
To view information about nodes in the OceanBase cluster, run the following statement:
obclient> use oceanbase Database changed obclient> select * from dba_ob_servers; +-------------+----------+----+--------------+----------+-----------------+--------+----------------------------+-----------+-----------------------+----------------------------+----------------------------+-------------------------------------------------------------------------------------------+ | SVR_IP | SVR_PORT | ID | ZONE | SQL_PORT | WITH_ROOTSERVER | STATUS | START_SERVICE_TIME | STOP_TIME | BLOCK_MIGRATE_IN_TIME | CREATE_TIME | MODIFY_TIME | BUILD_VERSION | +-------------+----------+----+--------------+----------+-----------------+--------+----------------------------+-----------+-----------------------+----------------------------+----------------------------+-------------------------------------------------------------------------------------------+ | 6.x.xxx.xx | 2882 | 6 | sa128_obv4_2 | 2881 | NO | ACTIVE | 2022-12-30 16:17:03.173519 | NULL | NULL | 2022-12-30 16:08:04.749100 | 2023-01-04 11:48:36.589270 | 4.0.0.0_101000022022120716-0d7927892ad6d830e28437af099f018b0ad9a322(Dec 7 2022 16:22:15) | | 6.x.xxx.xx | 2882 | 4 | sa128_obv4_3 | 2881 | NO | ACTIVE | 2022-12-30 16:36:35.567437 | NULL | NULL | 2022-12-30 16:08:02.755200 | 2023-01-04 14:13:36.976548 | 4.0.0.0_101000022022120716-0d7927892ad6d830e28437af099f018b0ad9a322(Dec 7 2022 16:22:15) | | 6.x.xxx.xxx | 2882 | 3 | sa128_obv4_3 | 2881 | NO | ACTIVE | 2022-12-12 12:42:00.054759 | NULL | NULL | 2022-11-03 15:37:09.530894 | 2022-12-22 14:43:26.717736 | 4.0.0.0_101000022022120716-0d7927892ad6d830e28437af099f018b0ad9a322(Dec 7 2022 16:22:15) | | 6.x.xx.xx | 2882 | 1 | sa128_obv4_1 | 2881 | NO | ACTIVE | 2022-12-12 12:25:17.555651 | NULL | NULL | 2022-11-03 15:37:08.990683 | 2022-12-12 12:25:18.553763 | 4.0.0.0_101000022022120716-0d7927892ad6d830e28437af099f018b0ad9a322(Dec 7 2022 16:22:15) | | 6.x.xx.xxx | 2882 | 2 | sa128_obv4_2 | 2881 | YES | ACTIVE | 2022-12-12 11:46:37.222980 | NULL | NULL | 2022-11-03 15:37:09.490511 | 2022-12-12 11:47:31.075335 | 4.0.0.0_101000022022120716-0d7927892ad6d830e28437af099f018b0ad9a322(Dec 7 2022 16:22:15) | | 6.x.xx.xx | 2882 | 5 | sa128_obv4_1 | 2881 | NO | ACTIVE | 2022-12-30 16:25:45.420996 | NULL | NULL | 2022-12-30 16:08:03.928478 | 2023-01-04 11:48:36.578231 | 4.0.0.0_101000022022120716-0d7927892ad6d830e28437af099f018b0ad9a322(Dec 7 2022 16:22:15) | +-------------+----------+----+--------------+----------+-----------------+--------+----------------------------+-----------+-----------------------+----------------------------+----------------------------+-------------------------------------------------------------------------------------------+ 6 rows in set (0.03 sec)It is recommended that dedicated O&M users run cluster O&M commands.
Cluster O&M commands can be executed through the system tenant. For example, run the following command to isolate an abnormal node:
obclient> ALTER SYSTEM STOP SERVER 'xx.xx.xx.xx:2882';After the command is executed, you can confirm whether the isolation is successful by checking the
STOP_TIMEfield of the node in theDBA_OB_SERVERSview.
Log on to a user tenant
A user tenant is created by a user. A user tenant can provide complete database services and supports MySQL and Oracle modes.
To view information on all tenants, log on as a system tenant and query the DBA_OB_TENANTS view.
TENANT_TYPEspecifies the tenant type.SYSis the system tenant,METAis a meta tenant, andUSERis a user tenant. The ID of the system tenant is 1. Among tenants whose ID is greater than 1000, even-numbered IDs indicate user tenants, and odd-numbered IDs indicate meta tenants. The ID of a user tenant is greater than that of its corresponding meta tenant by 1.COMPATIBILITY_MODEspecifies the tenant mode.MYSQLindicates MySQL mode andORACLEindicates Oracle mode.
In MySQL mode, both the MySQL client and OBClient can be used to log on to a user tenant. However, in Oracle mode, only the OBClient can be used to log on to a user tenant.
The database connection strings for logging in to a user tenant are almost identical to those for logging in to the sys tenant. The only difference is that you need to change the tenant name in the logon account.
For user tenants in MySQL mode, the built-in data dictionary views and dynamic performance views of OceanBase Database are all located in the oceanbase namespace. For user tenants in Oracle mode, the built-in views of OceanBase Database are located under the SYS user. The names, fields, and use experience of views are the same in both modes.
Log on to a meta tenant
Meta tenants are used for internal management in OceanBase Database. For each user tenant created, a corresponding meta tenant is automatically created whose lifecycle is the same as that of the user tenant. A meta tenant cannot be logged on directly, but its information can be accessed through the user tenant and system tenant.
More information
For more information about the methods and procedures for connecting to OceanBase Database, see: