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更新时间：2022-08-15 08:28:55
[20171121]rman backup as copy 2.txt
--//昨天测试backup as copy ,备份时备份文件的文件头什么时候更新.是最后完成后还是顺序写入备份文件.
--//我测试的数据文件使用数据文件2(表空间sysaux),也许是文件不够大,应该减慢备份速度来测试看看.
1.环境:
SCOTT@book> @ &r/ver1
PORT_STRING VERSION BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
$ cat dump_head.sh
#! /bin/bash
for i in $(seq 1000)
do
# echo $i
xxd -c32 -g 2 -s 8192 -l 32 $1 >> /tmp/dump_head.txt 2>/dev/null
sleep 1
done
2.测试:
--//首先启动dump_head.sh脚本,session 1:
$ . dump_head.sh /home/oracle/backup/tea01.dbf &
--//在sesion 2,在rman下执行备份:
RMAN> CONFIGURE CHANNEL 1 DEVICE TYPE DISK RATE 1M;
using target database control file instead of recovery catalog
new RMAN configuration parameters:
CONFIGURE CHANNEL 1 DEVICE TYPE DISK RATE 1 M;
new RMAN configuration parameters are successfully stored
RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET;
old RMAN configuration parameters:
CONFIGURE DEVICE TYPE DISK PARALLELISM 3 BACKUP TYPE TO BACKUPSET;
new RMAN configuration parameters:
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET;
new RMAN configuration parameters are successfully stored
--//设置DISK RATE 1M,这样可以减慢备份的速度,便于观察.并且仅仅打开1个并行.
RMAN> backup as copy datafile 6 format '/home/oracle/backup/%b';
Starting backup at 2017-11-21 09:43:09
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00006 name=/mnt/ramdisk/book/tea01.dbf
output file name=/home/oracle/backup/tea01.dbf tag=TAG20171121T094309 RECID=17 STAMP=960630229
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:45
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
channel ORA_DISK_1: throttle time: 0:00:40
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Finished backup at 2017-11-21 09:43:54
Starting Control File and SPFILE Autobackup at 2017-11-21 09:43:54
piece handle=/u01/app/oracle/fast_recovery_area/BOOK/autobackup/2017_11_21/o1_mf_s_960630234_f1716tsv_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 2017-11-21 09:43:55
--//注意看下划线内容,throttle time: 0:00:40.
throttle
英 [?θr?tl] 美 [?θrɑ:tl]
n.
节流阀;喉咙，气管;[机]风门
vt.& vi.
扼杀，压制;勒死，使窒息;使节流;（用节汽阀等）调节
vi.
节流，减速;窒息
-----------------------------------------------
--//而我的备份文件就是40M+8k的数据文件.
$ ls -lh /home/oracle/backup/tea01.dbf
-rw-r----- 1 oracle oinstall 41M 2017-11-21 09:43:49 /home/oracle/backup/tea01.dbf
$ ls -l /home/oracle/backup/tea01.dbf
-rw-r----- 1 oracle oinstall 41951232 2017-11-21 09:43:49 /home/oracle/backup/tea01.dbf
--//session 1:
$ fg
. dump_head.sh /home/oracle/backup/tea01.dbf
^C^
3.检查/tmp/dump_head.txt输出记录:
$ uniq -c /tmp/dump_head.txt
1 0002000: 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 ................................
40 0002000: 00a2 0000 0100 8001 0000 0000 0000 0105 81a6 0000 0000 0000 0000 0000 0000 0000 ................................
14 0002000: 0ba2 0000 0100 8001 0000 0000 0000 0104 61c1 0000 0000 0000 0004 200b 6e21 b74f ................a?....... .n!.O
--//^_^,再次验证我的判断.
--//从以上输出可以发现使用backup as copy备份,一定先建立一个空文件,输出一堆0000(需要大约1秒),大小与数据文件一致,这样可以先检测是否磁盘满足备份需求.
--//然后写入开头00a2,出现40次(我脚本执行sleep 1,不考虑其它消耗正好是40秒).
--//到最后才更新as copy方式的备份映像的文件头.
--//oracle的设计确实考虑许多因素,与备份文件集模式一样最后写入文件头信息,这样保证使用备份image是正确的,
--//设想一下,如果顺序写入备份image文件,如果备份过程中发生中断,而那这个image备份文件来恢复,会发生什么情况呢?
--//而现在这样设计意味着发生中断,备份image的文件头是"坏"的,意味着不能用于恢复.
--//还有一个疑问,写入备份image的文件头信息是 开始备份前读取的文件头信息,然后最后完成备份在读取文件头信息呢?
--//我只要在备份过程发出alter system checkpoint就知道.
--// 重复测试看看.
RMAN> delete datafilecopy all ;
SYS@book> SELECT file#, CHECKPOINT_CHANGE#, CHECKPOINT_TIME,CREATION_CHANGE# , RESETLOGS_CHANGE#,status, CHECKPOINT_COUNT,fuzzy,name,tablespace_name FROM v$datafile_header;
FILE# CHECKPOINT_CHANGE# CHECKPOINT_TIME CREATION_CHANGE# RESETLOGS_CHANGE# STATUS CHECKPOINT_COUNT FUZ NAME TABLESPACE_NAME
----- ------------------ ------------------- ---------------- ----------------- ------- ---------------- --- -------------------------------- ---------------
1 13279819419 2017-11-21 10:22:57 7 925702 ONLINE 1246 YES /mnt/ramdisk/book/system01.dbf SYSTEM
2 13279819419 2017-11-21 10:22:57 1834 925702 ONLINE 1247 YES /mnt/ramdisk/book/sysaux01.dbf SYSAUX
3 13279819419 2017-11-21 10:22:57 923328 925702 ONLINE 1156 YES /mnt/ramdisk/book/undotbs01.dbf UNDOTBS1
4 13279819419 2017-11-21 10:22:57 16143 925702 ONLINE 1243 YES /mnt/ramdisk/book/users01.dbf USERS
5 13279819419 2017-11-21 10:22:57 952916 925702 ONLINE 1152 YES /mnt/ramdisk/book/example01.dbf EXAMPLE
6 13279819419 2017-11-21 10:22:57 13276257767 925702 ONLINE 634 YES /mnt/ramdisk/book/tea01.dbf TEA
6 rows selected.
--//session 1:
RMAN> backup as copy datafile 6 format '/home/oracle/backup/%b';
Starting backup at 2017-11-21 10:26:10
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00006 name=/mnt/ramdisk/book/tea01.dbf
....等
--//session 2:
SYS@book> SELECT file#, CHECKPOINT_CHANGE#, CHECKPOINT_TIME,CREATION_CHANGE# , RESETLOGS_CHANGE#,status, CHECKPOINT_COUNT,fuzzy,name,tablespace_name FROM v$datafile_header;
FILE# CHECKPOINT_CHANGE# CHECKPOINT_TIME CREATION_CHANGE# RESETLOGS_CHANGE# STATUS CHECKPOINT_COUNT FUZ NAME TABLESPACE_NAME
----- ------------------ ------------------- ---------------- ----------------- ------- ---------------- --- -------------------------------- ----------------
1 13279819419 2017-11-21 10:22:57 7 925702 ONLINE 1246 YES /mnt/ramdisk/book/system01.dbf SYSTEM
2 13279819419 2017-11-21 10:22:57 1834 925702 ONLINE 1247 YES /mnt/ramdisk/book/sysaux01.dbf SYSAUX
3 13279819419 2017-11-21 10:22:57 923328 925702 ONLINE 1156 YES /mnt/ramdisk/book/undotbs01.dbf UNDOTBS1
4 13279819419 2017-11-21 10:22:57 16143 925702 ONLINE 1243 YES /mnt/ramdisk/book/users01.dbf USERS
5 13279819419 2017-11-21 10:22:57 952916 925702 ONLINE 1152 YES /mnt/ramdisk/book/example01.dbf EXAMPLE
6 13279819660 2017-11-21 10:26:10 13276257767 925702 ONLINE 635 YES /mnt/ramdisk/book/tea01.dbf TEA
--//注意看数据文件6的CHECKPOINT_CHANGE#=13279819660(备份开始前CHECKPOINT_CHANGE#=13279819419),说明在备份开始时要做文件检查点, 更新文件头scn.
SYS@book> alter system checkpoint ;
System altered.
SYS@book> alter system checkpoint ;
System altered.
SYS@book> alter system checkpoint ;
System altered.
--//在备份的过程中我发3次alter system checkpoint ;
--//session 1:
RMAN> backup as copy datafile 6 format '/home/oracle/backup/%b';
Starting backup at 2017-11-21 10:26:10
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00006 name=/mnt/ramdisk/book/tea01.dbf
output file name=/home/oracle/backup/tea01.dbf tag=TAG20171121T102610 RECID=19 STAMP=960632810
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:45
channel ORA_DISK_1: throttle time: 0:00:39
Finished backup at 2017-11-21 10:26:55
Starting Control File and SPFILE Autobackup at 2017-11-21 10:26:55
piece handle=/u01/app/oracle/fast_recovery_area/BOOK/autobackup/2017_11_21/o1_mf_s_960632816_f173qj22_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 2017-11-21 10:26:57
--//session 2:
SYS@book> SELECT file#, CHECKPOINT_CHANGE#, CHECKPOINT_TIME,CREATION_CHANGE# , RESETLOGS_CHANGE#,status, CHECKPOINT_COUNT,fuzzy,name,tablespace_name FROM v$datafile_header;
FILE# CHECKPOINT_CHANGE# CHECKPOINT_TIME CREATION_CHANGE# RESETLOGS_CHANGE# STATUS CHECKPOINT_COUNT FUZ NAME TABLESPACE_NAME
----- ------------------ ------------------- ---------------- ----------------- ------- ---------------- --- -------------------------------------------------- ------------------------------
1 13279819678 2017-11-21 10:26:26 7 925702 ONLINE 1249 YES /mnt/ramdisk/book/system01.dbf SYSTEM
2 13279819678 2017-11-21 10:26:26 1834 925702 ONLINE 1250 YES /mnt/ramdisk/book/sysaux01.dbf SYSAUX
3 13279819678 2017-11-21 10:26:26 923328 925702 ONLINE 1159 YES /mnt/ramdisk/book/undotbs01.dbf UNDOTBS1
4 13279819678 2017-11-21 10:26:26 16143 925702 ONLINE 1246 YES /mnt/ramdisk/book/users01.dbf USERS
5 13279819678 2017-11-21 10:26:26 952916 925702 ONLINE 1155 YES /mnt/ramdisk/book/example01.dbf EXAMPLE
6 13279819678 2017-11-21 10:26:26 13276257767 925702 ONLINE 638 YES /mnt/ramdisk/book/tea01.dbf TEA
6 rows selected.
--//看看备份写入的scn是13279819678还是13279819660呢?
BBED> p /d filename '/home/oracle/backup/tea01.dbf' block 1 kcvfh.kcvfhckp.kcvcpscn
struct kcvcpscn, 8 bytes @484
ub4 kscnbas @484 394917772
ub2 kscnwrp @488 3
BBED> p /d filename '/mnt/ramdisk/book/tea01.dbf' block 1 kcvfh.kcvfhckp.kcvcpscn
struct kcvcpscn, 8 bytes @484
ub4 kscnbas @484 394917790
ub2 kscnwrp @488 3
SYS@book> select power(2,32)*3+394917772 from dual ;
POWER(2,32)*3+394917772
-----------------------
13279819660
SYS@book> select power(2,32)*3+394917790 from dual ;
POWER(2,32)*3+394917790
-----------------------
13279819678
--//从CHECKPOINT_CHANGE#的scn号可以看出是备份文件的文件头信息是备份时读取的文件头信息,而不是经过多次alter system checkpint后的信息.
--//也就是备份时已经读取这部分信息到内存(下面的补充测试也说明问题),最后在写入备份image的文件头的.
--//我再次修改我的测试脚本,-s 8676对应的CHECKPOINT_CHANGE#号信息.再次重复测试,仅仅贴出结果.
$ cat dump_head.sh
#! /bin/bash
for i in $(seq 1000)
do
# echo $i
xxd -c32 -g 2 -s 8192 -l 32 $1 >> /tmp/dump_head.txt 2>/dev/null
xxd -c32 -g 2 -s 8676 -l 32 $1 >> /tmp/dump_head.txt 2>/dev/null
sleep 1
done
$ grep "^0002000:" /tmp/dump_head.txt | uniq -c
40 0002000: 00a2 0000 0100 8001 0000 0000 0000 0105 81a6 0000 0000 0000 0000 0000 0000 0000 ................................
39 0002000: 0ba2 0000 0100 8001 0000 0000 0000 0104 1292 0000 0000 0000 0004 200b 6e21 b74f .......................... .n!.O
$ grep "^00021e4:" /tmp/dump_head.txt | uniq -c
40 00021e4: 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 ................................
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
77 00021e4: 73fc 8917 0300 0000 f91b 4239 0100 0000 c003 0000 875a 0100 1000 313b 0200 0000 s?.....?B9....?...Z....1;....
--//可以看出前面40秒,根本没有写入文件头scn信息.最后才写入的.
--//收尾还原:
RMAN> configure channel 1 device type disk clear;
old RMAN configuration parameters:
CONFIGURE CHANNEL 1 DEVICE TYPE DISK RATE 1 M;
old RMAN configuration parameters are successfully deleted
released channel: ORA_DISK_1
RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 3 BACKUP TYPE TO BACKUPSET;
old RMAN configuration parameters:
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET;
new RMAN configuration parameters:
CONFIGURE DEVICE TYPE DISK PARALLELISM 3 BACKUP TYPE TO BACKUPSET;
new RMAN configuration parameters are successfully stored