Identifier length limits
| Item |
Maximum length |
| Cluster name |
128 bytes |
| Tenant name |
63 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 |
127 bytes |
| Type |
Maximum length |
| Cluster name |
128 bytes |
| Tenant name |
63 bytes |
| Username |
64 bytes |
| Table name |
128 bytes |
| Column name |
128 bytes |
| Index name |
128 bytes |
| View name |
128 bytes |
| Alias |
128 bytes |
| The name of the object. |
128 bytes |
| Table group name |
127 bytes |
Maximum number of connections of an OceanBase Database Proxy (ODP) cluster
| Type |
Upper limit |
| Number of connections of a single OceanBase Database Proxy (ODP) cluster |
You can specify the client_max_connections parameter of an ODP cluster to limit the number of connections of the ODP cluster. The default value is 8192.
Note
You can increase the number of ODP nodes or the value of the client_max_connections parameter to increase the maximum number of connections allowed for a cluster.
|
Maximum number of partition replicas
| Type |
Upper limit |
| Number of partition replicas for an OBServer node |
No upper limit.
Note
The number of partition replicas for each OBServer node can be estimated based on the size of the memory for the tenant. About 20,000 tablets are supported by 1 GB of memory.
|
Single-table limits
| Type |
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 |
- Oracle mode: 65,536
- MySQL mode: 8,192
|
Single-column limits
| Type |
Upper limit |
| Length of an index column |
16 KB |
String type limits
| Type |
Maximum length |
CHAR |
256 bytes |
VARCHAR |
262144 bytes |
BINARY |
256 bytes |
VARBINARY |
1048576 bytes |
TINYBLOB |
255 bytes |
BLOB |
65536 bytes |
MEDIUMBLOB |
16777216 bytes |
LONGBLOB |
536870911 bytes |
TINYTEXT |
256 bytes |
TEXT |
65536 bytes |
MEDIUMTEXT |
16777216 bytes |
LONGTEXT |
536870911 bytes |
| Type |
Maximum length |
CHAR |
2000 bytes |
NCHAR |
2000 bytes |
VARCHAR |
32767 bytes |
VARCHAR2 |
32767 bytes |
NVARCHAR2 |
32767 bytes |
BLOB |
536870911 bytes |
CLOB |
536870911 bytes |
Limitations
The following table describes the limitations of the Physical Standby Database feature.
| Item |
Description |
| Maximum number of standby tenants supported for a primary tenant |
Unlimited. |
| Homogeneous resources 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. |
| System 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 for the primary tenant, you must assess and determine whether to modify this parameter for the standby tenants. |
| System variables |
The system variables of the primary and standby tenants are physically synchronized. After you modify a system variable for the primary tenant, the system automatically modifies this system variable for the standby tenants. |
| Users and passwords |
You can create a user and change the password of a user only in the primary tenant. The updates in the primary tenant are synchronized to the standby tenants. |
| Read/write operations |
A standby tenant supports only read operations and does not support write operations. |
| Minor and major compactions |
The minor compactions for the primary tenant are independent of those for the standby tenants.
Independent major compactions are not supported for the standby tenants. The standby tenants synchronize major compaction information from the primary tenant. |
| Switchover |
To perform a switchover, all replicas in the log streams of the target standby tenant must be online. |
| Failover |
To perform a failover, all replicas in the log streams of the target standby tenant must be online. |
