The topic provides information on the limitations of various aspects in OceanBase Database. It is essential to consider these limitations while working with OceanBase Database to achieve optimal performance and prevent any possible issues or errors.
Identifier length
MySQL mode
Item Maximum length Cluster name 128 bytes Tenant name 64 bytes Username 64 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 128 bytes Oracle mode
Item Maximum length Cluster name 128 bytes Tenant name 64 bytes Username 64 bytes Table name 128 bytes Column name 128 bytes Index name 128 bytes View name 128 bytes Alias 255 bytes Object name 128 bytes Table group name 128 bytes
Maximum number of connections of an ODP
| Item | Upper limit |
|---|---|
| Number of connections of a single ODP | You can specify the client_max_connections parameter of an ODP to specify the maximum number of connections of the ODP. The default value is 8192. You can increase the number of ODP nodes or the value of the client_max_connections parameter to increase the maximum number of connections for a cluster.
|
Maximum number of partition replicas
| Item | Upper limit |
|---|---|
| Number of partition replicas of an OBServer node | No upper limit. Note You can estimate the number of partition replicas per OBServer node based on the memory size of the tenant. 1 GB of memory can support about 20,000 tablets. |
Single-table limits
| 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 | 1.5 MB |
| Total number of primary key columns | 64 |
| Primary key length | 16 KB |
| Number of partitions |
|
Single-column limits
| Item | Upper limit |
|---|---|
| Length of an index column | 262,143 bytes |
String type limits
MySQL mode
Oracle mode
| Type | Maximum length |
|---|---|
CHAR |
256 bytes |
VARCHAR |
1,048,576 bytes |
BINARY |
256 bytes |
VARBINARY |
1,048,576 bytes |
TINYBLOB |
255 bytes |
BLOB |
65536 bytes |
MEDIUMBLOB |
16,777,216 bytes |
LONGBLOB |
536,870,911 bytes |
TINYTEXT |
256 bytes |
TEXT |
65536 bytes |
MEDIUMTEXT |
16,777,216 bytes |
LONGTEXT |
536,870,911 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 |
536,870,911 bytes |
CLOB |
536,870,911 bytes |
Limitations on the physical standby database feature
The table below shows the limitations for using the physical standby database feature.
| Item | Description |
|---|---|
| Number of standby tenants | Unmlimited |
| Heterogeneity between the primary and standby tenants |
|
| Synchronization of parameter modifications between the primary tenant and standby tenant | Parameters of the primary tenant and standby tenant are independent and not physically synchronized. Therefore, when you modify a parameter for the primary tenant, evaluate whether the corresponding parameter for the standby tenant needs to be modified. |
| Synchronization of system variable modifications between the primary tenant and standby tenant | When modifications are made to system variables for the primary tenant, these modifications will be synchronized and applied to the corresponding system variables of the standby tenant. |
| Standby tenant operations |
|
| Switchover | Before you switch from a standby tenant to a primary tenant, make sure that:
|
| Failover | Before you perform failover, make sure that all servers in the cluster where the standby tenant is located are online. |