Verification Tasks

Scenarios

This section describes how to compare verification items to check if there are any differences between source and destination databases. To minimize the impact on services and shorten the service interruption duration, the following comparison methods are provided:

Object-level comparison: It compares databases, tables, and indexes.
Data-level row comparison: It compares the number of rows in the tables to be synchronized. This comparison method is recommended because it is fast.
Data-level static value comparison: It checks whether data in the synchronized table is consistent. The time required for comparison depends on the amount of data in the table.

Value comparison and row comparison cannot be performed at the same time.

Value comparison and object-level comparison cannot be performed at the same time.

Prerequisites

A verification task has been started.

Comparison Description

**Table 1** Data verification capability of each data flow
Synchronization Direction	Data Flow	Object-Level Comparison	Row Comparison	Account-Level Comparison	Static Value Comparison
To the cloud	MySQL -> MySQL	Supported	Supported	Not supported	Supported
To the cloud	MySQL -> PostgreSQL	Supported	Supported	Not supported	Not supported
To the cloud	MySQL -> GaussDB Distributed	Supported	Supported	Not supported	Supported
To the cloud	MySQL -> GaussDB Centralized	Supported	Supported	Not supported	Supported
To the cloud	MySQL -> TaurusDB	Supported	Supported	Not supported	Supported
To the cloud	PostgreSQL -> PostgreSQL	Supported	Supported	Supported	Supported
To the cloud	PostgreSQL -> GaussDB Centralized	Supported	Supported	Not supported	Supported
To the cloud	PostgreSQL -> GaussDB Distributed	Supported	Supported	Not supported	Supported
To the cloud	DDM -> MySQL	Supported	Supported	Not supported	Not supported
To the cloud	DDM -> DDM	Supported	Supported	Not supported	Not supported
To the cloud	Oracle -> MySQL	Supported	Supported	Not supported	Supported
To the cloud	Oracle -> TaurusDB	Supported	Supported	Not supported	Supported
To the cloud	Oracle -> GaussDB Centralized	Supported	Supported	Not supported	Supported
To the cloud	Oracle -> GaussDB Distributed	Supported	Supported	Not supported	Supported
To the cloud	Oracle -> DDM	Supported	Supported	Not supported	Not supported
To the cloud	Oracle > PostgreSQL	Supported	Supported	Not supported	Not supported
To the cloud	DB2 for LUW -> GaussDB Centralized	Supported	Supported	Not supported	Supported
To the cloud	DB2 for LUW -> GaussDB Distributed	Supported	Supported	Not supported	Supported
To the cloud	TiDB -> TaurusDB	Supported	Supported	Not supported	Not supported
To the cloud	Microsoft SQL Server -> GaussDB(DWS)	Supported	Supported	Not supported	Not supported
To the cloud	Microsoft SQL Server -> GaussDB Centralized	Supported	Supported	Not supported	Supported
To the cloud	Microsoft SQL Server -> GaussDB Distributed	Supported	Supported	Not supported	Supported
To the cloud	Microsoft SQL Server -> Microsoft SQL Server	Supported	Supported	Not supported	Not supported
To the cloud	MongoDB -> DDS	Supported	Supported	Not supported	Supported
To the cloud	MariaDB -> MariaDB	Supported	Supported	Not supported	Supported
To the cloud	MariaDB -> MySQL	Supported	Supported	Not supported	Supported
To the cloud	MariaDB -> TaurusDB	Supported	Supported	Not supported	Supported
To the cloud	TaurusDB -> TaurusDB	Supported	Supported	Not supported	Supported
To the cloud	Dynamo -> GeminiDB Dynamo	Supported	Not supported	Not supported	Not supported
Out of the cloud	MySQL -> MySQL	Supported	Supported	Not supported	Supported
Out of the cloud	MySQL -> CSS/ES	Supported	Supported	Not supported	Not supported
Out of the cloud	DDM -> MySQL	Supported	Supported	Not supported	Not supported
Out of the cloud	DDM -> Oracle	Supported	Supported	Not supported	Not supported
Out of the cloud	DDS -> MongoDB	Supported	Supported	Not supported	Supported
Out of the cloud	PostgreSQL -> PostgreSQL	Supported	Supported	Not supported	Supported
Out of the cloud	GaussDB Centralized -> MySQL	Supported	Supported	Not supported	Not supported
Out of the cloud	GaussDB Centralized -> Oracle	Supported	Supported	Not supported	Supported
Out of the cloud	GaussDB Centralized -> GaussDB Distributed	Supported	Supported	Not supported	Supported
Out of the cloud	GaussDB Centralized -> GaussDB Centralized	Supported	Supported	Not supported	Supported
Out of the cloud	GaussDB Centralized -> Informix	Supported	Supported	Not supported	Supported
Out of the cloud	GaussDB Centralized -> PostgreSQL	Supported	Supported	Not supported	Supported
Out of the cloud	GaussDB Distributed -> MySQL	Supported	Supported	Not supported	Not supported
Out of the cloud	GaussDB Distributed -> Oracle	Supported	Supported	Not supported	Supported
Out of the cloud	GaussDB Distributed -> GaussDB Distributed	Supported	Supported	Not supported	Not supported
Out of the cloud	GaussDB Distributed -> GaussDB Centralized	Supported	Supported	Not supported	Not supported
Out of the cloud	GaussDB Distributed -> PostgreSQL	Supported	Supported	Not supported	Supported
Out of the cloud	TaurusDB -> MySQL	Supported	Supported	Not supported	Supported
Out of the cloud	TaurusDB -> CSS/ES	Supported	Supported	Not supported	Not supported
Out of the cloud	TaurusDB -> Oracle	Supported	Supported	Not supported	Not supported
Out of the cloud	MariaDB -> MariaDB	Supported	Supported	Not supported	Supported
Self-built to self-built	Oracle -> GaussDB Centralized	Supported	Supported	Not supported	Supported
Self-built to self-built	Oracle -> GaussDB Distributed	Supported	Supported	Not supported	Supported
Self-built to self-built	MySQL -> CSS/ES	Supported	Supported	Not supported	Not supported
Self-built to self-built	MySQL -> GaussDB Centralized	Supported	Supported	Not supported	Not supported
Self-built to self-built	GaussDB Centralized -> Oracle	Supported	Supported	Not supported	Supported
Self-built to self-built	GaussDB Centralized -> GaussDB Centralized	Supported	Supported	Not supported	Not supported
Self-built to self-built	GaussDB Distributed -> Oracle	Supported	Supported	Not supported	Supported
Self-built to self-built	GaussDB Distributed -> GaussDB Distributed	Supported	Supported	Not supported	Not supported
Self-built to self-built	DB2 for LUW -> GaussDB Centralized	Supported	Supported	Not supported	Supported
Self-built to self-built	DB2 for LUW -> GaussDB Distributed	Supported	Supported	Not supported	Supported

Data comparison can clearly show whether data in the source database is different from that in the destination database. Currently, the following data types do not support value comparison, which will be skipped.

**Table 2** Data types that do not support value comparison
Source Database	Data Type
MySQL	TINYBLOB, BLOB, MEDIUMBLOB, LONGBLOB, TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT
GaussDB	TEXT, CLOB, BLOB, BYTEA, INTERVAL DAY TO SECOND, and INTERVAL
Oracle	BLOB, NCLOB, CLOB, LONG RAW, LONG, INTERVAL DAY TO SECOND, INTERVAL YEAR TO MONTH, UROWID, BFILE, XMLTYPE, and SDO_GEOMETRY
Microsoft SQL Server	TEXT, NTEXT, IMAGE, BINARY, VARBINARY, HIERARCHYID, XML, and TIMESTAMP
DB2 for LUW	CLOB, DBCLOB, BLOB, BINARY, VARBINARY, and TEXT
PostgreSQL	lob, text, byte, interval

DRS does not support value comparison if primary key columns contain the following data types, which will be grouped into a specified table that does not support comparison.

**Table 3** Primary key data types that do not support value comparison
Source Database	Data Type
MySQL	TINYBLOB, BLOB, MEDIUMBLOB, LONGBLOB, TINYTEXT, TEXT, MEDIUMTEXT, LONGTEXT, FLOAT, TIMESTAMP, DATE, and DATETIME
GaussDB	TEXT, CLOB, BLOB, BYTEA, INTERVAL DAY TO SECOND, INTERVAL, REAL, DOUBLE PRECISION, BOOL, TIME, TIMETZ, TIMESTAMP, TIMESTAMPTZ, and DATE
Oracle	BLOB, NCLOB, CLOB, LONG RAW, LONG, INTERVAL DAY TO SECOND, INTERVAL YEAR TO MONTH, UROWID, BFILE, XMLTYPE, SDO_GEOMETRY, BINARY_FLOAT, BINARY_DOUBLE, FLOAT, RAW, TIMESTAMP, TIMESTAMP WITH TIME ZONE, TIMESTAMP WITH LOCAL TIME ZONE, and DATE
Microsoft SQL Server	FLOAT, REAL, DATE, DATETIME, DATETIME2, DATETIMEOFFSET, TIME, TIMESTAMP, TEXT, NTEXT, IMAGE, BINARY, and VARBINARY
DB2 for LUW	CLOB, DBCLOB, BLOB, BINARY, VARBINARY, and TEXT

Creating a Comparison Task

On the Data Verification Management page, click the target task in the Task Name/ID column.
Click the Verification Tasks tab.
Select objects to be compared and create a comparison task.
- On the Object-Level Comparison tab page, click Compare. Wait for a while and click to check whether Consistent is displayed in the Result column for all comparison items. You can locate a comparison item and click View Details in the Operation column.
  Figure 1 Object-level comparison
- To create a data-level comparison task, click Create Comparison Task on the Data-Level Comparison tab page, specify Comparison Type and Object in the displayed dialog box, and click OK.
  Figure 2 Creating a data-level comparison task
  - Row: Check whether the number of rows in the source table is the same as that in the destination table.
  - Value: Check whether the source table has same data as the destination table.
    Static: This comparison method is applicable at off-peak hours when no data changes.
  - Object: Select objects to be compared.
- To create a comparison task when specified data needs to be filtered out, click the Data-Level Comparison tab, click Create Comparison Task, set Comparison Type and Comparison Method, and Enable Filter Data.
  Figure 3 Creating a comparison task when specified data needs to be filtered out
  
  Select objects and click Next. Select tables, enter filtering criteria, and click Verify.
  
  Figure 4 Selecting objects
  
  After the verification is complete, click Generate Processing Rule and click Yes to create a comparison task.
  
  Figure 5 Processing Rule
After the comparison creation task is submitted, the Data-Level Comparison tab is displayed. Click to refresh the list and view the comparison result of the specified comparison type.

Figure 6 Data-level comparison
- To view row or value comparison details, click View Results.
  Figure 7 Data-level comparison details
- Click Export Report to export the comparison report.
- Click Download to download the exported report to your local PC.
- You can also view comparison details of canceled comparison tasks.
- The exported report is retained for 24 hours. Download it to your local PC as soon as possible.