[20171205]关于rman output Memory Buffers 2.txt
--//昨天在QQ上与人聊天,再次提到这个问题.感觉在链接http://blog.itpub.net/267265/viewspace-2147866/上的说服力不强.
--//我当时仅仅想说明oracle的备份是顺序读取数据文件的.
--//另外在链接http://blog.itpub.net/267265/viewspace-2147878/提到:
■ If the number of files being multiplexed is greater than eight, then RMAN allocates four
buffers of size 128KB. This ensures that each file being backed up will account for 512KB
of buffer memory.
--//按照对方的理解,这个规则不存在,如果一个备份集参数filesperset>8 ,实际上按照filesperset=8来操作,先解决8个数据文件,
--//然后在解决8个,如此循环,我的理解对方的说法是对的.此时的输入缓存是512K.
--//最后做一次测试说明 output Memory Buffers是1M.对方的疑惑是如果多个文件(>4)输入缓存是512K,如何说明output Memory
--//Buffers是1M呢?
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
SCOTT@book> show parameter filesystemio_options
NAME TYPE VALUE
-------------------- ------ -----
filesystemio_options string NONE
--//注:使用异步IO,strace跟踪的结果有一点不会看,不知道写出的IO量.我的测试没有使用异步IO.
$ cat d2.txt
drop tablespace t01 including contents and datafiles;
drop tablespace t02 including contents and datafiles;
drop tablespace t03 including contents and datafiles;
drop tablespace t04 including contents and datafiles;
drop tablespace t05 including contents and datafiles;
CREATE TABLESPACE T01 DATAFILE '/mnt/ramdisk/book/T01.dbf' SIZE 6M AUTOEXTEND OFF LOGGING ONLINE EXTENT MANAGEMENT LOCAL AUTOALLOCATE BLOCKSIZE 8K SEGMENT SPACE MANAGEMENT AUTO FLASHBACK ON;
CREATE TABLESPACE T02 DATAFILE '/mnt/ramdisk/book/T02.dbf' SIZE 6M AUTOEXTEND OFF LOGGING ONLINE EXTENT MANAGEMENT LOCAL AUTOALLOCATE BLOCKSIZE 8K SEGMENT SPACE MANAGEMENT AUTO FLASHBACK ON;
CREATE TABLESPACE T03 DATAFILE '/mnt/ramdisk/book/T03.dbf' SIZE 6M AUTOEXTEND OFF LOGGING ONLINE EXTENT MANAGEMENT LOCAL AUTOALLOCATE BLOCKSIZE 8K SEGMENT SPACE MANAGEMENT AUTO FLASHBACK ON;
CREATE TABLESPACE T04 DATAFILE '/mnt/ramdisk/book/T04.dbf' SIZE 6M AUTOEXTEND OFF LOGGING ONLINE EXTENT MANAGEMENT LOCAL AUTOALLOCATE BLOCKSIZE 8K SEGMENT SPACE MANAGEMENT AUTO FLASHBACK ON;
CREATE TABLESPACE T05 DATAFILE '/mnt/ramdisk/book/T05.dbf' SIZE 6M AUTOEXTEND OFF LOGGING ONLINE EXTENT MANAGEMENT LOCAL AUTOALLOCATE BLOCKSIZE 8K SEGMENT SPACE MANAGEMENT AUTO FLASHBACK ON;
create table t01 tablespace t01 as select rownum id ,to_char(rownum,'FM000000')||lpad('A',26,'A') name from dual connect by level<=1e5;
create table t02 tablespace t02 as select rownum id ,to_char(rownum,'FM000000')||lpad('B',26,'B') name from dual connect by level<=1e5;
create table t03 tablespace t03 as select rownum id ,to_char(rownum,'FM000000')||lpad('C',26,'C') name from dual connect by level<=1e5;
create table t04 tablespace t04 as select rownum id ,to_char(rownum,'FM000000')||lpad('D',26,'D') name from dual connect by level<=1e5;
create table t05 tablespace t05 as select rownum id ,to_char(rownum,'FM000000')||lpad('E',26,'E') name from dual connect by level<=1e5;
alter system checkpoint;
alter system checkpoint;
alter system checkpoint;
RMAN> report schema ;
using target database control file instead of recovery catalog
Report of database schema for database with db_unique_name BOOK
List of Permanent Datafiles
===========================
File Size(MB) Tablespace RB segs Datafile Name
---- -------- -------------------- ------- ------------------------
1 760 SYSTEM *** /mnt/ramdisk/book/system01.dbf
2 940 SYSAUX *** /mnt/ramdisk/book/sysaux01.dbf
3 1075 UNDOTBS1 *** /mnt/ramdisk/book/undotbs01.dbf
4 256 USERS *** /mnt/ramdisk/book/users01.dbf
5 346 EXAMPLE *** /mnt/ramdisk/book/example01.dbf
6 40 TEA *** /mnt/ramdisk/book/tea01.dbf
7 6 T01 *** /mnt/ramdisk/book/T01.dbf
8 6 T02 *** /mnt/ramdisk/book/T02.dbf
9 6 T03 *** /mnt/ramdisk/book/T03.dbf
10 6 T04 *** /mnt/ramdisk/book/T04.dbf
11 6 T05 *** /mnt/ramdisk/book/T05.dbf
List of Temporary Files
=======================
File Size(MB) Tablespace Maxsize(MB) Tempfile Name
---- -------- -------------------- ----------- --------------------
1 414 TEMP 32767 /mnt/ramdisk/book/temp01.dbf
RMAN> CONFIGURE CHANNEL 1 DEVICE TYPE DISK clear ;
using target database control file instead of recovery catalog
old RMAN configuration parameters:
CONFIGURE CHANNEL 1 DEVICE TYPE DISK RATE 128 K;
old RMAN configuration parameters are successfully deleted
RMAN> CONFIGURE CONTROLFILE AUTOBACKUP OFF;
old RMAN configuration parameters:
CONFIGURE CONTROLFILE AUTOBACKUP ON;
new RMAN configuration parameters:
CONFIGURE CONTROLFILE AUTOBACKUP OFF;
new RMAN configuration parameters are successfully stored
--//注:设置CONTROLFILE AUTOBACKUP OFF;,主要目的避免对测试干扰.
2.测试:
$ strace -f -o /tmp/t12345.txt rlrman target /
Recovery Manager: Release 11.2.0.4.0 - Production on Tue Dec 5 15:14:05 2017
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database: BOOK (DBID=1337401710)
RMAN> backup datafile 7,8,9,10,11 format '/home/oracle/backup/T12345_%U' ;
Starting backup at 2017-12-05 15:14:11
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=132 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00007 name=/mnt/ramdisk/book/T01.dbf
input datafile file number=00008 name=/mnt/ramdisk/book/T02.dbf
input datafile file number=00009 name=/mnt/ramdisk/book/T03.dbf
input datafile file number=00010 name=/mnt/ramdisk/book/T04.dbf
input datafile file number=00011 name=/mnt/ramdisk/book/T05.dbf
channel ORA_DISK_1: starting piece 1 at 2017-12-05 15:14:12
channel ORA_DISK_1: finished piece 1 at 2017-12-05 15:14:13
piece handle=/home/oracle/backup/T12345_h1slc8e4_1_1 tag=TAG20171205T151412 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2017-12-05 15:14:13
Starting Control File and SPFILE Autobackup at 2017-12-05 15:14:14
piece handle=/u01/app/oracle/fast_recovery_area/BOOK/autobackup/2017_12_05/o1_mf_s_961946054_f2dkt67x_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 2017-12-05 15:14:15
RMAN> quit
Recovery Manager complete.
$ grep "pwrite(263" /tmp/t12345.txt
23434 pwrite(263, "\23\242\0\0\1\0\0\0\243\207t\27\3\0\1\4c\235\0\0\0\4 \v\0\4 \vn!\267O"..., 1040384, 8192) = 1040384
23434 pwrite(263, "\36\242\0\0\200\0@\2\331\205t\27\3\0\1\4>\245\3\0\t\0\0\0\200\0\0\0\0\0\0\0"..., 1048576, 1048576) = 1048576
23434 pwrite(263, "\36\242\0\0\200\0\300\2A\204t\27\3\0\1\4\276U\5\0\v\0\0\0\200\0\37\0\0\0\0\0"..., 1048576, 2097152) = 1048576
23434 pwrite(263, "\36\242\0\0\200\0\0\2\224\201t\27\3\0\1\4*W\2\0\10\0\0\0\200\0\17\2\0\0\0\0"..., 1048576, 3145728) = 1048576
23434 pwrite(263, "\36\242\0\0\200\0\200\2\262\203t\27\3\0\1\4\256W\4\0\n\0\0\0\200\0\17\2\0\0\0\0"..., 1048576, 4194304) = 1048576
23434 pwrite(263, "\6\242\0\0\200\0\300\1G\205t\27\3\0\2\4\266 \1\0\1\0\0\0\334b\1\0@\205t\27"..., 1048576, 5242880) = 1048576
23434 pwrite(263, "\6\242\0\0\200\0@\2\267\205t\27\3\0\2\4\266 \3\0\1\0\0\0\336b\1\0\260\205t\27"..., 1048576, 6291456) = 1048576
23434 pwrite(263, "\6\242\0\0\200\0\300\2!\206t\27\3\0\2\4\216 \5\0\1\0\0\0\340b\1\0\32\206t\27"..., 1048576, 7340032) = 1048576
23434 pwrite(263, "\6\242\0\0\200\0\0\2\222\205t\27\3\0\2\4\3606\2\0\1\0\0\0\335b\1\0{\205t\27"..., 1048576, 8388608) = 1048576
23434 pwrite(263, "\6\242\0\0\200\0\200\2\374\205t\27\3\0\2\4\3646\4\0\1\0\0\0\337b\1\0\345\205t\27"..., 1048576, 9437184) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\300\1c\205t\27\3\0\2\4\3468\1\0\1\0\0\0\334b\1\0@\205t\27"..., 1048576, 10485760) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1@\2\323\205t\27\3\0\2\4\3468\3\0\1\0\0\0\336b\1\0\260\205t\27"..., 1048576, 11534336) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\300\2=\206t\27\3\0\2\4\3368\5\0\1\0\0\0\340b\1\0\32\206t\27"..., 1048576, 12582912) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\0\2\236\205t\27\3\0\2\4\0007\2\0\1\0\0\0\335b\1\0{\205t\27"..., 1048576, 13631488) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\200\2\10\206t\27\3\0\2\4\0047\4\0\1\0\0\0\337b\1\0\345\205t\27"..., 1048576, 14680064) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\300\1e\205t\27\3\0\2\4i:\1\0\1\0\0\0\334b\1\0@\205t\27"..., 1048576, 15728640) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1@\2\325\205t\27\3\0\2\4i:\3\0\1\0\0\0\336b\1\0\260\205t\27"..., 1048576, 16777216) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\300\2?\206t\27\3\0\2\4Q:\5\0\1\0\0\0\340b\1\0\32\206t\27"..., 1048576, 17825792) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\0\2\240\205t\27\3\0\2\4\302\244\2\0\1\0\0\0\335b\1\0{\205t\27"..., 1048576, 18874368) = 1048576
23434 pwrite(263, "\6\242\0\0\200\1\200\2\n\206t\27\3\0\2\4\306\244\4\0\1\0\0\0\337b\1\0\345\205t\27"..., 1048576, 19922944) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2\300\1h\205t\27\3\0\2\4h=\1\0\1\0\0\0\334b\1\0@\205t\27"..., 1048576, 20971520) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2@\2\330\205t\27\3\0\2\4h=\3\0\1\0\0\0\336b\1\0\260\205t\27"..., 1048576, 22020096) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2\300\2B\206t\27\3\0\2\4P=\5\0\1\0\0\0\340b\1\0\32\206t\27"..., 1048576, 23068672) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2\0\2\243\205t\27\3\0\2\4\2672\2\0\1\0\0\0\335b\1\0{\205t\27"..., 1048576, 24117248) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2\200\2\r\206t\27\3\0\2\4\2632\4\0\1\0\0\0\337b\1\0\345\205t\27"..., 1048576, 25165824) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2\300\1k\205t\27\3\0\2\4\302\225\1\0\1\0\0\0\334b\1\0@\205t\27"..., 1048576, 26214400) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2@\2\333\205t\27\3\0\2\4\302\225\3\0\1\0\0\0\336b\1\0\260\205t\27"..., 1048576, 27262976) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2\300\2E\206t\27\3\0\2\4\372\225\5\0\1\0\0\0\340b\1\0\32\206t\27"..., 1048576, 28311552) = 1048576
23434 pwrite(263, "\6\242\0\0\200\2\0\2\247\205t\27\3\0\2\4\234|\2\0\1\0\0\0\335b\1\0{\205t\27"..., 983040, 29360128) = 983040
--//注:后面还有一点输出,不是这个对备份文件的,应该是控制文件的更新.
--//可以发现除了前面,中间都是写出1048576,也就是1M的.
$ sed 's/^.*=//g' /tmp/tx.txt | xargs echo | sed 's/ /+/g' | bc -l
30334976
$ ls -l /home/oracle/backup/T12345_h1slc8e4_1_1
-rw-r----- 1 oracle oinstall 30343168 2017-12-05 15:14:13 /home/oracle/backup/T12345_h1slc8e4_1_1
--//30343168-30334976 = 8192,相差第1块(OS块),备份集文件第0块也是OS块,跟数据文件一样的.
$ strings T12345_h1slc8e4_1_1 | egrep "AAAAA|BBBBB|CCCCC|DDDDD|EEEEE" | cut -c20-30| uniq -c
9978 AAAAAAAAAAA
9978 BBBBBBBBBBB
9978 CCCCCCCCCCC
9978 DDDDDDDDDDD
9978 EEEEEEEEEEE
10080 AAAAAAAAAAA
10080 BBBBBBBBBBB
10080 CCCCCCCCCCC
10080 DDDDDDDDDDD
10080 EEEEEEEEEEE
10416 AAAAAAAAAAA
10416 BBBBBBBBBBB
10416 CCCCCCCCCCC
10416 DDDDDDDDDDD
10416 EEEEEEEEEEE
10752 AAAAAAAAAAA
10752 BBBBBBBBBBB
10752 CCCCCCCCCCC
10752 DDDDDDDDDDD
10752 EEEEEEEEEEE
10416 AAAAAAAAAAA
10416 BBBBBBBBBBB
10416 CCCCCCCCCCC
10416 DDDDDDDDDDD
10416 EEEEEEEEEEE
10752 AAAAAAAAAAA
10752 BBBBBBBBBBB
10752 CCCCCCCCCCC
10752 DDDDDDDDDDD
10752 EEEEEEEEEEE
10416 AAAAAAAAAAA
10416 BBBBBBBBBBB
10416 CCCCCCCCCCC
10416 DDDDDDDDDDD
10416 EEEEEEEEEEE
10752 AAAAAAAAAAA
10752 BBBBBBBBBBB
10752 CCCCCCCCCCC
10752 DDDDDDDDDDD
10752 EEEEEEEEEEE
10416 AAAAAAAAAAA
10416 BBBBBBBBBBB
10416 CCCCCCCCCCC
10416 DDDDDDDDDDD
10416 EEEEEEEEEEE
6022 AAAAAAAAAAA
6022 BBBBBBBBBBB
6022 CCCCCCCCCCC
6022 DDDDDDDDDDD
6022 EEEEEEEEEEE
SCOTT@book> select * from dba_extents where segment_name='T01';
OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME EXTENT_ID FILE_ID BLOCK_ID BYTES BLOCKS RELATIVE_FNO
------ ------------ ------------ --------------- ---------- ---------- ---------- ---------- ---------- ------------
SCOTT T01 TABLE T01 0 7 128 65536 8 7
SCOTT T01 TABLE T01 1 7 136 65536 8 7
SCOTT T01 TABLE T01 2 7 144 65536 8 7
SCOTT T01 TABLE T01 3 7 152 65536 8 7
SCOTT T01 TABLE T01 4 7 160 65536 8 7
SCOTT T01 TABLE T01 5 7 168 65536 8 7
SCOTT T01 TABLE T01 6 7 176 65536 8 7
SCOTT T01 TABLE T01 7 7 184 65536 8 7
SCOTT T01 TABLE T01 8 7 192 65536 8 7
SCOTT T01 TABLE T01 9 7 200 65536 8 7
SCOTT T01 TABLE T01 10 7 208 65536 8 7
SCOTT T01 TABLE T01 11 7 216 65536 8 7
SCOTT T01 TABLE T01 12 7 224 65536 8 7
SCOTT T01 TABLE T01 13 7 232 65536 8 7
SCOTT T01 TABLE T01 14 7 240 65536 8 7
SCOTT T01 TABLE T01 15 7 248 65536 8 7
SCOTT T01 TABLE T01 16 7 256 1048576 128 7
SCOTT T01 TABLE T01 17 7 384 1048576 128 7
SCOTT T01 TABLE T01 18 7 512 1048576 128 7
SCOTT T01 TABLE T01 19 7 640 1048576 128 7
20 rows selected.
SCOTT@book> select count(*) from t01 where DBMS_ROWID.ROWID_BLOCK_NUMBER (rowid) between 128 and 128+64-1 ;
COUNT(*)
----------
9978
--//占64K(512K).虽然每个文件的输入缓存512K,但是还是达到1M才写入备份文件的.
3.还有一个方法可以证明输出是1M.
RMAN> CONFIGURE CHANNEL 1 DEVICE TYPE DISK RATE 128 K;
using target database control file instead of recovery catalog
new RMAN configuration parameters:
CONFIGURE CHANNEL 1 DEVICE TYPE DISK RATE 128 K;
new RMAN configuration parameters are successfully stored
--//建立测试脚本:
$ cat tt.sh
#! /bin/bash
rman target / <<EOF &
backup datafile 7,8,9,10,11 format '/home/oracle/backup/XX12345_%U' ;
EOF
sleep 7
cachedel /home/oracle/backup/XX12345*
cachedel /home/oracle/backup/XX12345*
for i in {1 .. 240 }
do
cachestats /home/oracle/backup/XX12345* >> /tmp/XX.txt
sleep 1
done
--//注选择cachestats这样执行快,对测试影响小一些.
$ uniq -c /tmp/XX.txt
3 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 0/7688 (0.0%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 254/7688 (3.3%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 510/7688 (6.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 766/7688 (10.0%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 1022/7688 (13.3%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 1278/7688 (16.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 1534/7688 (20.0%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 1790/7688 (23.3%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 2046/7688 (26.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 2302/7688 (29.9%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 2558/7688 (33.3%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 2814/7688 (36.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 3070/7688 (39.9%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 3326/7688 (43.3%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 3582/7688 (46.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 3838/7688 (49.9%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 4094/7688 (53.3%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 4350/7688 (56.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 4606/7688 (59.9%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 4862/7688 (63.2%) [filesize=30752.0K, pagesize=4K]
7 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 5118/7688 (66.6%) [filesize=30752.0K, pagesize=4K]
1 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 5190/7688 (67.5%) [filesize=30752.0K, pagesize=4K]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 5374/7688 (69.9%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 5630/7688 (73.2%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 5886/7688 (76.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 6142/7688 (79.9%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 6398/7688 (83.2%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 6654/7688 (86.6%) [filesize=30752.0K, pagesize=4K]
8 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 6910/7688 (89.9%) [filesize=30752.0K, pagesize=4K]
16 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 7166/7688 (93.2%) [filesize=30752.0K, pagesize=4K]
6 /home/oracle/backup/XX12345_h6slcas0_1_1 pages in cache: 7408/7408 (100.0%) [filesize=29632.0K, pagesize=4K]
--//利用cachestats看备份文件缓存的特性(开始要清除缓存,不然一直是100%).写入时同时缓存,这样2行相差基本都是256.注意OS的块大
--//小4K.(除了开始与结束)
--//256*4 = 1024K.
--//另外你可以发现最后每次出现8行,每次出现8行,8*128(配置rman DISK RATE 128 K) 也正好是 1024K.
--//下划线的地方是一点点小意外,查看时正好写入.^_^.
--//最后2行你还可以发现实际上备份文件变小1点点.
--//这也是这个系列的最后一篇,不再这个问题上再纠结了.
