SQL Guide : Database system tables and system views : System tables for data synchronization : SYS_SYNC_HISTORY_COLUMNS
  
SYS_SYNC_HISTORY_COLUMNS
If you turn on synchronization history for a table, you may turn it on for all columns, or only for a subset of columns. If you turn it on for a subset of columns, then the SYS_SYNC_HISTORY_COLUMNS table records which columns you are keeping synchronization history information for. There is one row in SYS_SYNC_HISTORY_COLUMNS for each column that you keep synchronization history for.
Column name
Description
REL_ID
The ID of the table to keep sync history for.
COLUMN_NUMBER
The ordinal number of the column in that table that we keep sync history for. (For example, if we keep sync history for the second column in the table, then this field will hold the number 2.
See also
System tables for data synchronization