Cluster name length
| Item | Maximum length |
|---|---|
| Cluster name | 128 bytes |
Identifier length
MySQL mode
Oracle mode
| Item | Maximum length |
|---|---|
| Username | 64 bytes |
| Tenant name | 63 bytes |
| Database name | 128 bytes |
| Table name | 64 characters |
| Column name | 128 bytes |
| Index name | 64 bytes |
| View name | 64 bytes |
| Alias | 255 bytes |
| Table group name | 127 bytes |
| User-defined variable | 64 characters |
| Item | Maximum length |
|---|---|
| Username | 64 bytes |
| Table name | 128 bytes |
| Column name | 128 bytes |
| Index name | 128 bytes |
| View name | 128 bytes |
| Alias | 128 bytes |
| Object name | 128 bytes |
| Table group name | 127 bytes |
ODP connections
Connections to databases
When you connect to OceanBase Database V4.x by using OceanBase Database Proxy (ODP), free routing between primary and standby databases is not supported.
Maximum number of connections
| Item | Upper limit |
|---|---|
| Number of connections per ODP | It is specified by the client_max_connections parameter of ODP. The default value is 8192.
NoteYou can increase the number of ODP nodes or the value of the |
Maximum number of partition replicas
| Item | Upper limit |
|---|---|
| Number of partition replicas per OBServer node | Unlimited.
NoteYou can estimate the number of partition replicas of each OBServer node based on the memory size of the tenant. 1 GB of memory supports about 20,000 tablets. |
Single table
| Item | Upper limit |
|---|---|
| Row length | 1.5 MB |
| Number of columns | 4,096 |
| Number of indexes | 128 |
| Total number of index columns | 512 |
| Index length | 16 KB |
| Total number of primary key columns | 64 |
| Primary key length | 16 KB |
| Number of partitions |
|
Single column
| Item | Upper limit |
|---|---|
| Length of an index column | 16 KB |
String type
MySQL mode
Oracle mode
| Item | Maximum length |
|---|---|
CHAR |
256 characters |
VARCHAR |
262,144 characters |
BINARY |
256 bytes |
VARBINARY |
1,048,576 bytes |
TINYBLOB |
255 bytes |
BLOB |
65,535 bytes |
MEDIUMBLOB |
16,777,215 bytes |
LONGBLOB |
536,870,910 bytes |
TINYTEXT |
255 bytes |
TEXT |
65,535 bytes |
MEDIUMTEXT |
16,777,215 bytes |
LONGTEXT |
536,870,910 bytes |
| Item | Maximum length |
|---|---|
CHAR |
2,000 bytes |
NCHAR |
2,000 bytes |
VARCHAR |
32,767 bytes |
VARCHAR2 |
32,767 bytes |
NVARCHAR2 |
32,767 bytes |
BLOB |
536,870,910 bytes |
CLOB |
536,870,910 bytes |
Feature usage
Shared storage
In the current version, the following limitations apply to OceanBase clusters with the shared-storage (SS) architecture:
- Multi-region deployment is not supported.
- The columnar storage engine is not supported.
- The physical standby database feature is not supported.
- The
data_disk_sizeof a tenant cannot be reduced. - At most 100,000 partitions are supported.
Physical standby databases
The following table describes the limitations on the physical standby database feature.
| Item | Description |
|---|---|
| Maximum number of standby tenants supported by one primary tenant | Unlimited. |
| Whether homogeneous resources are required for the primary and standby tenants | Resources of the primary and standby tenants do not need to be homogeneous. We recommend that you use the same resource specifications for the primary and standby tenants. |
| Parameters | The parameters of the primary tenant are independent of those of a standby tenant, and parameter modifications are not physically synchronized. After you modify a parameter of the primary tenant, you must assess whether to modify the corresponding parameter of the standby tenants. |
| System variables | System variables of the primary and standby tenants are physically synchronized. If you modify a system variable of the primary tenant, the system synchronously modifies the corresponding system variable of the standby tenants. |
| Users and passwords | You can create users and change user passwords only in the primary tenant. The updated information is synchronized to the standby tenants. |
| Read and write operations | A standby tenant supports only read operations. |
| Minor and major compactions | Minor compactions in the primary tenant are independent of those in the standby tenants. Major compactions are not performed in a standby tenant. Instead, the major compaction information is synchronized from the primary tenant to the standby tenants. |
| Switchover | All replicas of log streams of the standby tenants must be online. |
| Failover | All replicas of log streams of the standby tenants must be online. |
