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doc-exports/docs/drs/umn/drs_16_1161.html
Wang , Deng Ke 5523220f09 DRS UMN 20221102 version 
Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com>
Co-authored-by: Wang , Deng Ke <wangdengke2@huawei.com>
Co-committed-by: Wang , Deng Ke <wangdengke2@huawei.com>
2022-12-08 10:16:13 +00:00

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What Impact Does a DRS Comparison Task Have on Databases?

  • Object comparison: System tables of the source and destination databases are queried, occupying about 10 sessions. The database is not affected. However, if there are a large number of objects (for example, hundreds of thousands of tables), the database may be overloaded.
  • Row comparison: The number of rows in the source and destination databases is queried, which occupies about 10 sessions. The SELECT COUNT statement does not affect the database. However, if a table contains a large amount of data (hundreds of millions of records), the database will be overloaded and the query results will be returned slowly.
  • Value comparison: All data in the source and destination databases is queried, and each field is compared. The query pressure on the database leads to high I/O. The query speed is limited by the I/O and network bandwidth of the source and destination databases. Value comparison occupies one or two CPUs, and about 10 sessions.
Parent topic: Data-Level Comparison