679 bytes sent via SQL*Net to client
589 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
3 rows processed
SYS@ORCL>delete test_db1 where owner='tyger';
3 rows deleted.
Execution Plan
----------------------------------------------------------
Plan hash value: 3135214910
-------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------
| 0 | DELETE STATEMENT | | 8 | 136 | 154 (2)| 00:00:02 |
| 1 | DELETE | TEST_DB1 | | | | |
|* 2 | TABLE ACCESS FULL| TEST_DB1 | 8 | 136 | 154 (2)| 00:00:02 |
-------------------------------------------------------------------------------
Predicate Information (identified by operation id):
2 - filter("OWNER"='tyger')
Note
-----
- dynamic sampling used for this statement
Statistics
----------------------------------------------------------
4 recursive calls
3 db block gets
769 consistent gets
0 physical reads
1064 redo size
679 bytes sent via SQL*Net to client
567 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
3 rows processed
结论：对于占用多个段的大表来说，可能对数据修改时 对 数据字典 或者对于区、块的分配都包含在 physical reads中。
感想：
对于生产库来说，这个值一般不会太考虑到底数字是怎么来的，因为数字都比较大，一般只在乎它的大小数量级。