先来看一个参数,影响数据库恢复的时间
SYS@ orcl>show parameter mttr
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
fast_start_mttr_target integer 0
这个参数影响我们做恢复时所用的时间,如果设置了该值,数据库就会保证恢复数据的时间不会超过所设定的值(也就是说会根据数据库自己测算的写脏块的速度,调整内存脏数据写到日志文件中的频率)
下面我们看下归档日志的存放路径
SYS@ orcl>show parameter recovery
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string +FLASH
db_recovery_file_dest_size big integer 15882M
recovery_parallelism integer 0
查看闪回区的使用情况
SYS@ orcl>col name for a20
SYS@ orcl>col space_limit for 99999999999
SYS@ orcl>select * from v$recovery_file_dest;
NAME SPACE_LIMIT SPACE_USED SPACE_RECLAIMABLE NUMBER_OF_FILES
-------------------- ------------ ---------- ----------------- ---------------
+FLASH 16653484032 171966464 0 4
Elapsed: 00:00:00.01
也可以换成MB显示
SYS@ orcl>select name,SPACE_LIMIT/1048576,SPACE_USED/1048576 from v$recovery_file_dest;
NAME SPACE_LIMIT/1048576 SPACE_USED/1048576
-------------------- ------------------- ------------------
+FLASH 15882 164
Elapsed: 00:00:00.03
闪回区里面还可以存放数据库关键文件的镜像
SYS@ orcl>select * from v$controlfile;
STATUS NAME IS_ BLOCK_SIZE FILE_SIZE_BLKS
------- -------------------------------------------------- --- ---------- --------------
+DATA/orcl/controlfile/current.260.982157551 NO 16384 594
+FLASH/orcl/controlfile/current.256.982157551 YES 16384 594
Elapsed: 00:00:00.00
SYS@ orcl>select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIME
---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ------------------
NEXT_CHANGE# NEXT_TIME
------------ ------------------
1 1 10 52428800 512 2 NO CURRENT 1110841 23-JUL-18
2.8147E+14
2 1 8 52428800 512 2 NO INACTIVE 1095134 23-JUL-18
1103706 23-JUL-18
3 1 9 52428800 512 2 NO INACTIVE 1103706 23-JUL-18
1110841 23-JUL-18
Elapsed: 00:00:00.02
SYS@ orcl>select * from v$logfile;
GROUP# STATUS TYPE MEMBER IS_
---------- ------- ------- -------------------------------------------------- ---
3 ONLINE +DATA/orcl/onlinelog/group_3.263.982157555 NO
3 ONLINE +FLASH/orcl/onlinelog/group_3.259.982157557 YES
2 ONLINE +DATA/orcl/onlinelog/group_2.262.982157553 NO
2 ONLINE +FLASH/orcl/onlinelog/group_2.258.982157555 YES
1 ONLINE +DATA/orcl/onlinelog/group_1.261.982157551 NO
1 ONLINE +FLASH/orcl/onlinelog/group_1.257.982157553 YES
6 rows selected.
Elapsed: 00:00:00.01
SYS@ orcl>archive log list
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 8
Current log sequence 10
SYS@ orcl>