| DATABASE REFRESH AND COMPARE UTILITIES |
In addition to actual replication (capturing changes and applying them to another database) HVR supports refresh and compare utilities. Database refresh is when two databases need to be brought into sync with each other. Database compare allows the operator to see whether two large databases are identical or not. These are important and handy utilities for managing replication.
Bulk Compare
HVR performs checksums on each of the replicated tables and only compares these checksums. This allows big databases to be compared without any network traffic.
Bulk Refresh
HVR reads the data from all the tables in one database and bulk-loads it into the target database. If the databases are on different machines then the data is automatically compressed and uncompressed as it passes through the network pipe. Table indexes are then reset.
Row-wise Compare
HVR reads from one database and compares each row with the corresponding row in the other database. As this is done it calculates an SQL script describing the minimum insert, update and deletes statements needed to synchronize the table. If the databases are on different machines then the data is automatically compressed and uncompressed as it passes through the network pipe.
Row-wise Refresh
Row-wise refresh is the same as row-wise compare, except the resulting SQL statements are applied directly to the target database in order to re-synchronize the tables.
All these flavors of refresh and compare are very fast and very flexible. Even higher speeds can be achieved with an option to put database tables into groups and then refresh or compare these groups in parallel.
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