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SQL Anywhere 12.0.0 (Français) » SQL Remote » Creating SQL Remote systems » Understanding transaction log-based replication » Data types

 

BLOBs

BLOBs include the LONG VARCHAR, LONG BINARY, TEXT, and IMAGE data types.

When SQL Remote replicates an INSERT or UPDATE statement, it uses a variable in place of the BLOB value. That is, the BLOB is broken into pieces and replicated in chunks. At the recipient database, the pieces are reconstituted by using a SQL variable and concatenated. The value of the variable is built up by a sequence of statements of the form:

SET vble = vble || 'more_stuff';

The variable makes the size of the SQL statements involving long values smaller, so they fit within a single message.

The SET statements are separate SQL statements, so that the BLOB is effectively split over several SQL Remote messages.

 Controlling replication of BLOBs
 Using the verify_threshold option to minimize message size
 Using a work table to avoid redundant updates
 See also