[20161101]環境變數ORA_RMAN_SGA_TARGET

[20161101]環境變數ORA_RMAN_SGA_TARGET.txt

--如果資料庫恢復，需要啟動資料庫到nomount，如果沒有spfile檔案，在sqlplus是無法啟動的。
--在rman環境下，可以啟動到nomount，解決雞與蛋的問題，有一個環境變數ORA_RMAN_SGA_TARGET控制sga大小。

--測試看看：

1.環境：
SYS@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

--關閉資料庫，改名spfile檔案，如果存在init檔案也改名。

$ cd  /u01/app/oracle/product/11.2.0.4/dbhome_1/dbs
$ mv spfilebook.ora spfilebook.ora_20161101

2.啟動看看:
--可以設定引數可以改變sga記憶體大小.
export ORA_RMAN_SGA_TARGET=512

SYS@book> startup nomount
ORA-01078: failure in processing system parameters
LRM-00109: could not open parameter file '/u01/app/oracle/product/11.2.0.4/dbhome_1/dbs/initbook.ora'

--在sqlplus無法啟動到nomount.

RMAN> startup nomount

startup failed: ORA-01078: failure in processing system parameters
LRM-00109: could not open parameter file '/u01/app/oracle/product/11.2.0.4/dbhome_1/dbs/initbook.ora'

starting Oracle instance without parameter file for retrieval of spfile
Oracle instance started

Total System Global Area     534462464 bytes
Fixed Size                     2254952 bytes
Variable Size                272631704 bytes
Database Buffers             251658240 bytes
Redo Buffers                   7917568 bytes

SYS@book> show sga
Total System Global Area  534462464 bytes
Fixed Size                  2254952 bytes
Variable Size             272631704 bytes
Database Buffers          251658240 bytes
Redo Buffers                7917568 bytes

SYS@book> show parameter sga_target
NAME        TYPE          VALUE
----------- ------------- ---------
sga_target  big integer   512M

--可以發現SGA使用512M。與設定相符。

2.如果不設定呢？

$ export ORA_RMAN_SGA_TARGET=
$ rlrman
Recovery Manager: Release 11.2.0.4.0 - Production on Tue Nov 1 08:10:54 2016
Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.
connected to target database (not started)

RMAN> startup nomount
startup failed: ORA-01078: failure in processing system parameters
LRM-00109: could not open parameter file '/u01/app/oracle/product/11.2.0.4/dbhome_1/dbs/initbook.ora'

starting Oracle instance without parameter file for retrieval of spfile
Oracle instance started

Total System Global Area    1068937216 bytes
Fixed Size                     2260088 bytes
Variable Size                301990792 bytes
Database Buffers             754974720 bytes
Redo Buffers                   9711616 bytes

--可以發現SGA_TARGET使用1024M.我一直想設定有什麼用，難道有可能出現太小或者太多無法啟動的情況嗎？

3. 測試恢復spfile檔案。一般spfile這個時候也有問題，必須先恢復pfile，再轉成spfile格式。

RMAN> restore spfile to pfile '/tmp/b.oar' from autobackup;
Starting restore at 2016-11-01 08:12:56
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=1345 device type=DISK

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 11/01/2016 08:12:57
RMAN-06495: must explicitly specify DBID with SET DBID command

--//原來這樣需要指定dbid，第一次遇到這種情況。

RMAN> set dbid 1337401710
executing command: SET DBID

RMAN> restore spfile to pfile '/tmp/b.oar' from autobackup;
Starting restore at 2016-11-01 08:19:29
using channel ORA_DISK_1

channel ORA_DISK_1: looking for AUTOBACKUP on day: 20161101
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20161031
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20161030
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20161029
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20161028
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20161027
channel ORA_DISK_1: looking for AUTOBACKUP on day: 20161026
channel ORA_DISK_1: no AUTOBACKUP in 7 days found
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 11/01/2016 08:19:31
RMAN-06172: no AUTOBACKUP found or specified handle is not a valid copy or piece

--奇怪不知道為什麼不行。實際上我喜歡直接指定路徑，這樣就不需要設定dbid了。

$ rlrman
Recovery Manager: Release 11.2.0.4.0 - Production on Tue Nov 1 08:21:03 2016
Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.
connected to target database: DUMMY (not mounted)

RMAN> restore spfile to pfile '/tmp/b.oar' from '/u01/app/oracle/fast_recovery_area/BOOK/autobackup/2016_11_01/o1_mf_s_926756227_d1hqr3pw_.bkp';
Starting restore at 2016-11-01 08:21:52
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=1345 device type=DISK

channel ORA_DISK_1: restoring spfile from AUTOBACKUP /u01/app/oracle/fast_recovery_area/BOOK/autobackup/2016_11_01/o1_mf_s_926756227_d1hqr3pw_.bkp
channel ORA_DISK_1: SPFILE restore from AUTOBACKUP complete
Finished restore at 2016-11-01 08:21:54

$ head /tmp/b.oar
book.__db_cache_size=394264576
book.__java_pool_size=12582912
book.__large_pool_size=37748736
book.__oracle_base='/u01/app/oracle'#ORACLE_BASE set from environment
book.__pga_aggregate_target=209715200
book.__sga_target=637534208
book.__shared_io_pool_size=0
book.__shared_pool_size=213909504
book.__streams_pool_size=0
*._cursor_bind_capture_area_size=2001