15_oracle_admin_ configuration and archiving of online redo log files

First, Configuring redolog File

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There are the following errors in the configuration:

1. asymmetric,Group3 has only one member, which can result in write errors;

2. put multiple members of a group on one disk, so that not only the load that is frequently written is concentrated on one disk, but also does not realize the redundancy of the disk and does not play the role of backup.

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For the configuration of the online redo log file, the following recommendations are available:

1. with multiple sets of Redo LogFile, each group of at least two members, different members on different disks (even if a member of a group is damaged, as long as one member is normal, the database will still work). The specific number according to the specific situation, if the data concurrency is large, then the Redolog file data growth is very fast, you need to match a few groups, so that you can ensure that the Redolog file has been written to save data in a timely manner.

2. The online redo log file does nothave to be placed on a disk with an archive file (Archive) file to prevent LGWR and ARCn from working on a disk at the same time.

3. The data file (datafile) should not be placed on a disk with the Redo Log file.

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if the number of disks is larger, it is recommended that different group members be placed on separate disks, and that groups and groups will be evenly distributed to disk, similarly to The Control File is also applicable.

second, the application OMF to manage Redo Log File

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Iii. How to obtain group and group membership information for online redo logs

Sql> select * from V$logfile;

     GROUP# STATUS  TYPE   MEMBER                                 is_----------------------------------------------- ----- -----------------          3          ONLINE /oracle/oradata/orcl/redo03.log         NO         2          ONLINE /oracle/oradata/orcl/redo02.log         NO         1          online /oracle/oradata/orcl/redo01.log        no

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Sql> Select group#, thread#, members, archived, status from V$log;

    GROUP#    THREAD#   MEMBERS ARC  STATUS---------- ---------- ---------- --- ----------------          1          1           1 NO INACTIVE          2          1          1  NO INACTIVE         3           1          1  NO INACTIVE         4           1          2 NO  Current

Sql> select * from V$log_history;

recid stamp thread# sequence# first_change#first_tim next_change#---------- ---- ------ ---------- ---------- ---------------------- RESETLOGS_CHANGE#  Resetlogs----------------- ---------         1   854822167          1           1        754488 05-AUG-14        788787           75448805 -aug-14          2  854822200          1          2         788787 05-aug-14       792507            75448805-aug-14          3   854823639          1           3        792507 05-AUG-14        802814            75448805-aug-14

For more information on the Dynamic performance table for online redo log files, you can review the online documentation Reference get.

Iv. threads thread in the online redo log file Concept

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Thread is primarily used in a RAC environment, a multi-instance system, where each instance can have its own thread.

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V. Archived online redo log files

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Archive mode ensures data recovery and supports hot backup. The database default is non -Archive mode, but it is strongly recommended to use Archive mode in a production environment . Dynamic performance Tables v$instance and v$database can be used to query whether the current database is archive mode:

Sql> desc v$instance

 Name                                       Null?    Type -------------------------------------------------  ------------------- INSTANCE_NUMBER                                      NUMBER PARALLEL                                            varchar2 (3)  THREAD#                                             NUMBER ARCHIVER                                             VARCHAR2 (7) ...  blocked                                             VARCHAR2 (3)

Sql> Select Archiver from V$instance;

ARCHIVE-------STOPPED

sql> desc v$database;

 Name                                       Null?    Type -------------------------------------------------  ------------------- DBID                                                 number  NAME                                                VARCHAR2 (9)  PRIOR_RESETLOGS_TIME                                 DATE LOG_MODE                                            VARCHAR2 (12) ...  SUPPLEMENTAL_LOG_DATA_PL                            VARCHAR2 (3)  MIN_ required_capture_change#                        number

Sql> select Log_mode from V$database;

Log_mode------------Noarchivelog

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ARCn This process reads the online redo log file and writes it to the archive file. When the archive is complete, a corresponding record is added to the controlfile.

Non- in Archive mode, the online redo log file can be reused only when the checkpoint occurs, and in Archive mode, in addition to the checkpoint, you need to ensure that the file has been ARCn archived,Redo Log File can only be reused.

Archived online redo log files can also be multiplexed.

This article is from the "Big sword without front of the great Qiao Not Work" blog, please make sure to keep this source http://wuyelan.blog.51cto.com/6118147/1558315

15_oracle_admin_ configuration and archiving of online redo log files