Which Data Types are not Supported for Content Comparison?
Fields of the following data types are excluded from the comparison:
When a MySQL database serves as the source database: TINYBLOB, BLOB, MEDIUMBLOB, LONGBLOB, TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT.
When a PostgreSQL database serves as the source database: custom DOMAIN or TYPE.
During content comparison, tables with the following characteristics are automatically skipped:
The table is an empty table that contains no data.
The table has no primary key, unique field, or unique index.
The primary key, unique field, or unique index of the table is a composite one that consists of multiple fields.
The fields that consist of the primary key, unique field, and unique index are not of the following data types:The primary key, unique field, or unique index of the table is excluded from the following types:
When a MySQL database serves as the source database: TINYINT, SMALLINT, MEDIUMINT, INT (INTEGER), BIGINT, CHAR, VARCHAR, FLOAT, DOUBLE, and DECIMAL.
When a PostgreSQL database serves as the source database: SMALLINT (INT2), INT (INT4 and INTEGER), BIGINT (INT8), CHAR, BPCHAR, VARCHAR, UUID, DECIMAL (NUMERIC), FLOAT4 (REAL), and FLOAT8 (DOUBLE PRECISION).
Does a Data Audit Task Affect the Source and Destination Databases?
Object comparison: DTS queries system tables in the source and destination databases to obtain information about the compare objects. If a small number of objects need to be compared, the object comparison task has rare impacts on the databases. If a large number of objects need to be compared, the object comparison task may increase the workloads on the databases, and the comparison duration is long.
Row count comparison: When DTS runs the SELECT COUNT statement to query the number of rows in tables in the source database and the destination database, it requires up to 16 sessions. In most cases, the row count comparison task has minor impacts on the databases. If a large number of rows need to be compared, the row count comparison task may increase the workloads on the databases, and the comparison duration is long.
Content comparison: When DTS queries and compares all supported types of data in the source database and the destination database, it requires up to 32 sessions. This may increase the workloads on the databases. We recommend that you perform content comparison during off-peak hours.
How Long Does DTS Requires to Complete a Data Audit Task?
Object comparison: In most cases, DTS can complete an object comparison task in minutes. If a large number of objects need to be compared, the task duration increases.
Row count comparison: The query speed and database performance affect the comparison task duration. If a large number of rows need to be compared, the task duration is long.
Content comparison: The database performance and network condition affects the comparison task duration. If a large volume of data need to compared, the task duration is long.