Restrictions

This article introduces some current usage restrictions of the MDB system, and it is necessary to pay attention to avoiding related scenarios during the actual synchronization process.

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Mixed case scenarios

1. For all source databases, if there are mixed-case name scenarios and the values are the same after ignoring the case, an error will be reported during source streaming data parsing.
2. Object names or Schema names containing a dot (.) are not supported

Oracle

1. Oracle Logmnr cannot fetch large object field (xml, clob, nclob, blob) data, table without primary key will not carry LOB field filters in update/delete operation, which may result in deletion of multiple rows, or update of multiple rows.
2. Data synchronization of LONG/LONG RAW types is not supported. If these two types of columns exist in the table, an error will be reported during the data synchronization process.
3. extra-long interval year to month (999999999-11) in Oracle does not supported in openGauss
4. extra-long precision timestamp(9) in Oracle, but maximum timestamp(6) supported in openGauss

MySQL

1. The maximum total length of a single row cannot exceed 65,535 bytes (excluding text/blob related types).
2. The length of a single character field cannot exceed 65,535 bytes. For varchar of the utf8mb4 character set, its length cannot exceed 16,384.
3. The total length of the primary key and unique key cannot exceed 767 bytes.
4. timestamp field in openGauss/MogDB synchronized to datetime in MySQL will lose the time zone information and the time will be transferred to MySQL database time zone time
5. When sync openGauss/MogDB to GaussDB and MySQL version below 8.0, rename column statement is not supported, this type of DDL will report an error and require manual intervention

PostgreSQL

1. decodebuf: long timestamp (294276-01-01) synchronization of data will be abnormal
2. time data (24:00:00) is supported in PG, but not in MDB (Java)