(四.六)Direct Load(直接加载)
*.If archiving is enabled then direct load blocks are written to redo
*.In Oracle 9.2 each block requires a 19.1 and 24.2 change
*.直接加载比传统的insert 产生的redo少很多,如下例是32条记录,但是ITL就3个就搞定,如果传统的话估计要32个itl(多个session)
eg:
SQLLDR直接加载file#4,block 3404

------------------------
alter system dump logfile '/opt/ora_log/FSXYBAK/onlinelog/o1_mf_2_54n7c6mn_.log' dba min 4 3404 dba max 4 3404';
..........
.........
REDO RECORD - Thread:1 RBA: 0x000080.00014791.0110 LEN: 0x2024 VLD: 0x01
SCN: 0x0000.0029a44b SUBSCN: 1 10/31/2009 15:46:56
CHANGE #1 TYP:1 CLS: 1 AFN:4 DBA:0x01000d4c OBJ:43812 SCN:0x0000.0029a44b SEQ: 1 OP:19.1
Direct Loader block redo entry                                                        --Eirect Loader
Block header dump: 0x00000000
Object id on Block? Y
seg/obj: 0xab24 csc: 0x00.29a44a itc: 3 flg: E typ: 1 - DATA
     brn: 0 bdba: 0x1000d49 ver: 0x01 opc: 0
     inc: 0 exflg: 0

Itl           Xid                  Uba         Flag Lck        Scn/Fsc
0x01   0xffff.000.00000000 0x00000000.0000.00 C---    0 scn 0x0000.0029a44a
0x02   0x0000.000.00000000 0x00000000.0000.00 ----    0 fsc 0x0000.00000000
0x03   0x0000.000.00000000 0x00000000.0000.00 ----    0 fsc 0x0000.00000000
----------------------------------

(四.七)Nologging of redo
1.Redo generation can be disabled for some operations using
*.UNRECOVERABLE (Oracle 7)
*.NOLOGGING (Oracle 8.0 and above)                                                                     -->Nologging 可以防止redo产生
*.Objects created using NOLOGGING cannot be recovered                                                  -->Nologging 创建的对象将不可恢复
*.Backup should be taken immediately affect using NOLOGGING
*.ALTER TABLESPACE /database FORCE LOGGING;                                           -->强制logging
                                           -->Nologging后得立即备份
2.Nologging可以在哪些场合使用
Can be enabled for
specific tables and indexes at object level or statement level                                         -->可以在表和索引的对象和语句级别使用nologging
eg:
create index/table xxx nologging;

The following redo log entry indicates a range of blocks which cannot be recovered:
这些范围的块不能恢复
-------------
REDO RECORD - Thread:1 RBA: 0x003674.00000006.01e0 LEN: 0x0028 VLD: 0x01
SCN: 0x0000.00ebaeec SUBSCN: 1 05/09/2003 11:16:07
CHANGE #1 INVLD AFN:5 DBA:0x0142ff03 BLKS:0x001f SCN:0x0000.00ebaeec SEQ: 1 OP:19.2
Direct Loader invalidate block range redo entry                                                        -->直接加载的无效块范围的 redo entry                                               -->

------------
Nologgin 的相关操作以及对照10000row for test
Redo size in bytes
Operation                        LOGGING NOLOGGING
CREATE TABLE AS SELECT          14238844 39548
ALTER TABLE MOVE                14227236 45340
INSERT /*+ APPEND */            14221904 42452
CREATE MATERIALIZED VIEW        20726784 3784532
CREATE INDEX                    2042532 24548
ALTER INDEX REBUILD              2056440 32192
ALTER INDEX REBUILD ONLINE      2083832 67840
SQL*Loader (Direct)              14248116 56712
Online Reorganization            21330788 7169472

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