The provided steps in the DB2 Online schema update steps are not in the proper order. Step 4 and 5 shall be moved after Step 1. 

https://debezium.io/documentation/reference/2.2/connectors/db2.html#db2-hot-schema-update

Procedure when adding a column to the end of a table

1. Lock the source tables whose schema you want to change.
2. In the ASN register table, mark the locked tables as INACTIVE.
3. Reinitialize the ASN capture service.
4. Apply all changes to the schemas for the source tables.
5. Apply all changes to the schemas for the corresponding change-data tables.
6. In the ASN register table, mark the source tables as ACTIVE.
7. Reinitialize the ASN capture service.
8. Optional. Restart the connector to see updated column names in change events.

The expected order is the following:

1. Lock the source tables whose schema you want to change.
2. Apply all changes to the schemas for the source tables.
3. Apply all changes to the schemas for the corresponding change-data tables.
4. In the ASN register table, mark the locked tables as INACTIVE.
5. Reinitialize the ASN capture service.
6. In the ASN register table, mark the source tables as ACTIVE.
7. Reinitialize the ASN capture service.
8. Optional. Restart the connector to see updated column names in change events.

The integration test are also using these steps instead of what is written in the current documentation. 
https://github.com/debezium/debezium-connector-db2/blob/5ac3895b6ed42fff4e850ef7eb39448047ed986f/src/test/java/io/debezium/connector/db2/Db2OnlineDefaultValueIT.java

The Other documentation sections Procedure when adding a column to the middle of a table  and Offline schema update are likely have the same / similar issues.