title: Liquibase: Change column to an autoincrement column (identity) in DB2
body: <p>I'm trying to change a BIGINT Column to an autoincremented column in DB2 but I can't seem find how.
  I tried doing it like this:</p>
  
  <pre><code>    &lt;changeSet id="08.01" author="..."&gt;
          &lt;addColumn tableName="table_name"&gt;
              &lt;column name="id" type="bigint"&gt;
                  &lt;constraints nullable="true"/&gt;
              &lt;/column&gt;
  
              &lt;column name="member_type" type="varchar(100)"&gt;
                  &lt;constraints nullable="true"/&gt;
              &lt;/column&gt;
          &lt;/addColumn&gt;
      &lt;/changeSet&gt;
  
      &lt;changeSet id="08.02" author="..."&gt;
          &lt;addAutoIncrement tableName="table_name"
                            columnDataType="bigint"
                            columnName="id"/&gt;
      &lt;/changeSet&gt;
  </code></pre>
  
  <p>and when it runs I get this error:</p>
  
  <pre><code>org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'liquibase' defined in class path resource [org/springframework/boot/autoconfigure/liquibase/LiquibaseAutoConfiguration$LiquibaseConfiguration.class]: Invocation of init method failed; nested exception is liquibase.exception.MigrationFailedException: Migration failed for change set classpath:db/changelog/08-separation.xml::08.01::author:
       Reason: liquibase.exception.DatabaseException: DB2 SQL Error: SQLCODE=-270, SQLSTATE=42997, SQLERRMC=72, DRIVER=4.13.127 [Failed SQL: ALTER TABLE SCHEMATEST.table_name ALTER COLUMN id SET GENERATED BY DEFAULT AS IDENTITY]
      at org.springframework.bean
  ...
  ...
  ...
  Caused by: liquibase.exception.MigrationFailedException: Migration failed for change set classpath:db/changelog/08separation.xml::08.01::author:
       Reason: liquibase.exception.DatabaseException: DB2 SQL Error: SQLCODE=-270, SQLSTATE=42997, SQLERRMC=72, DRIVER=4.13.127 [Failed SQL: ALTER TABLE SCHEMATEST.table_name ALTER COLUMN id SET GENERATED BY DEFAULT AS IDENTITY]
  ...
  ...
  ...
  Caused by: com.ibm.db2.jcc.am.SqlSyntaxErrorException: DB2 SQL Error: SQLCODE=-270, SQLSTATE=42997, SQLERRMC=72, DRIVER=4.13.127
  </code></pre>