ROW MIGRATION 테스트

Question

제품 : ORACLE SERVER
작성날짜 : 2003-08-04
여기서는 row migration을 테스트 할 수 있는 방법을 알아 본다.
개요>
- migration을 테스트 할 수 있는 테이블을 만든다.
- 이전 데이타보다 훨씬 큰 데이타로 update한다.
- 테이블을 analyze하여 migration이 일어난 row들을 알아낸다.
- 임시 테이블을 만들어 상기 row를 저장한다.
- 원래의 테이블에서 migration이 일어난 row들을 삭제한다.
- 임시 테이블의 내용을 원래의 테이블에 insert 한다.
SQL> create table chain (name varchar2(100));
SQL> insert into chain values('a');
SQL> insert into chain select * from chain;
SQL> /
SQL> /
SQL> update chain set name = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
256 rows updated
SQL> commit;
SQL> @?/rdbms/admin/utlchain /* chained_rows table 생성 */
SQL> analyze table chain list chained rows;
SQL> select count(*) from chained_rows; /* chained, migrated rows
확인 */
SQL> create table chained_temp as select * from chain
2 where rowid in (select head_rowid from chained_rows
3 where table_name = 'CHAIN');
SQL> delete from chain
2 where rowid in (select head_rowid from chained_rows
3 where table_name = 'CHAIN');
SQL> insert into chain select * from chain_temp;
SQL> commit;
SQL> delete from chained_rows;
SQL> commit;
SQL> analyze table chain list chained rows;
SQL> select * from chained_rows;
no row selected
Reference Documents
<Note:122020.1>

Answer 1

in this case the concept is row chaining: "Oracle Database stores the data for the row in a chain of one or more data blocks reserved for the segment. Row chaining most often occurs with large rows. Examples include rows that contain a column of data type LONG or LONG RAW, a VARCHAR2(4000) column in a 2 KB block, or a row with a huge number of columns. Row chaining in these cases is unavoidable." http://docs.oracle.com/cd/E11882_01/server.112/e25789/logical.htm#sthref1529