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OpenEdge Change Data Capture Guide
CDC Schema : Change Table

Change Table

The Change Table schema has two parts: metadata fields to tie the change table to the original record, and column data specified by the policy definition.
The metadata portion of the change table contains the fields described in the table that follows.
Table 12. Change table metadata
Transaction number used to create this record.
timestamp tz
UTC timestamp and zone of the database server.
Number indicating an operation’s capture order within an object.
Support for larger than 32K record sizes.
*0 — no continuation
*Nonzero indicates last successfully processed field.
Used in conjunction with _Continuation-Position to identify an element of an array field.
If a Non-zero value, it is the array index of the element.
This value means a fragmented field is either present or not.
*0 —This field is not split into 2 records.
*1 — This field is split into 2 records.
The remainder of the record, the column data, is defined by the source table fields defined in the CDC policy. The general format is as follows:
User Data Columns specific to Source Table. The name of the field is taken from the Source table field that was selected.
Source Field Data type
Value from Source Table at the time of capture
The indexes for the Change Tracking tables are described in the following table.
Table 13. Change Table indexes
Index Name
Index Field
1 _Change-Sequence
2 _Operation
3 _Continuation
A CDC mandated index to establish a (foreign key) relationship to the Change Tracking Table. This index provides easy access to a chain of change records through the _Change-Sequence field.
1 User Defined Column
15 User Defined End Column
2 _Change-Sequence
Non Unique
Optional index created when the policy is defined and fields are picked to become part of the the identifying field index (_Identifying-Fields). This index is completely defined when the policy is designed, including index component order. A final component is added to the identifying field index, the _Change-Sequence field to preserves order.
1 _Time-Stamp
2 _Change-Sequence
Non Unique
A CDC mandated index that allows access to the Change Table through a combination of change sequence and a timestamp. This index promotes time sequencing of changes within a table (object).