Skip to main content

DB – Archive log mode


Versao Portuguesa





This post comes out from the practice to learn and preparation the subjects for OCP - Oracle Certified Professional . In simple words, Oracle works with logs, all DMS/DDL are written in log file, know as redo logs, the written happens in circular way. So the files are redo file contents will be replaced, with the transactions. In order to keep that info, Oracle allows to archive the contents.

It has a few reasons to archive the redo log, for now let focus on one, teh need of recover the database. I mean some thing happened and is need to put the database back. The traditional method is done in two steps.

1) Restore - restore data files and control files
2) Recover - Apply logs, in this case the archive logs .. and eventually redo log

Let's see how to do that, but for now a note, the database should be in mount state and in a consistent manner, eg after a "shutdown immediate". 





SQL> select startup_time from  v$instance;
STARTUP_Time
---------
19-DEC-12

SQL> select dbid,name,log_mode,flashback_on from  v$database;

      DBID        NAME       LOG_MODE          FLASHBACK_ON
----------          ---------      ------------               ------------------
1272537938 ORCL        NOARCHIVELOG   NO

SQL>  archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     6
Current log sequence           8

SQL>  alter system  switch logfile;
System altered.

SQL>  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

SQL> shut immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup mount;
ORACLE instance started.

Total System Global Area  577511424 bytes
Fixed Size                  1338000 bytes
Variable Size             364905840 bytes
Database Buffers          205520896 bytes
Redo Buffers                5746688 bytes
Database mounted.

SQL> alter database archivelog;
Database altered.

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     10
Next log sequence to archive   12
Current log sequence           12

SQL> alter database open;
Database altered.

SQL> select dbid,name,log_mode,flashback_on from  v$database;

      DBID         NAME                              LOG_MODE     FLASHBACK_ON
----------           ------------------------------ ------------          ------------------
1272537938  ORCL                                ARCHIVELOG   NO






Thank you for reading, hope this post was helpful.
Rogerio


Labels:

Comments

Post a Comment

Popular posts from this blog

DB - How to monitor Oracle datapump jobs

These days there is lot of work around database migrations not only but mainly to cloud providers. One of the ways to migrate Oracle databases is using data pump (expdp/impdp). In general works fine, it allows an easy way to bring the database even different OS. It is always good to monitor the progress, to know where we are and estimate how long we are from the end. In this post, I am sharing some queries to help with database monitoring progress. The queries can be easily tailed to various scenarios. Starting with a simple one - the track the number of objects loaded during an import operation. When there is a massive amount of errors during the import. Drop and run the import again. The bellow query can be useful also to monitor the number of objects if we are dropping the users. Here, I’m making the assumption there were no other database activity in progress on the last 24 hours. select owner, count(0) from dba_objects where owner in ( select username from dba_users where created...
Post a Comment
Read more

VM - Partilhar Pastas Windows - Linux

Neste post escrevo como partilhar pastas entre Windows (Host) e uma VM Guest, neste caso Linux. Ha algumas formas de fazer isto, esta parece me a mais facil. Seleccionar a Pasta Windows Na consola Virtual Box > Devices > Shared Folder Seleccionar a pasta windows para partilhar no Linux   O   Montar a pasta Windows na VM Ha duas opcoes : 1) Reiniciar a VM (Auto-mount) 2) Linha de comando [root@host ~]# mkdir -p /u01/stage/win_ebs_sw [root@host ~]# chmod 777 /u01/stage/win_ebs_sw [root@host ~]# mount -t vboxsf Oracle_EBS /u01/stage/win_ebs_sw/ [root@host ~]# ls /u01/stage/win_ebs_sw ebs_weblogic_webtier [root@host ~]# df -h /u01/stage/win_ebs_sw Filesystem Size Used Avail Use% Mounted on Oracle_EBS 895G 494G 401G 56% /u01/stage/win_ebs_sw Guardar a Configuracao no /etc/fstab para tornar as alteracoes permanentes. [root@host ~]# echo "Oracle_EBS /u01/stage/win_ebs_sw vboxsf defaults 0 0" >> /etc/fstab [root@host ~]# cat /etc/fstab # /etc/...
Post a Comment
Read more

DB – How to monitor Oracle database long ops ?

As DBAs, some questions we are often asked and to be fair we ask ourselfs when we are doing massive operations, are : Is the database doing something? How long the database takes to complete the task? There a data dictionary view, GV$SESSION_LONGOPS whom is really usefull for monitoring and to provide estimated time to get the task done. Starting with a first example, a query for general propose . set lines 240 col message form a100 col opname form a50 select * from ( select round(l.sofar/l.totalwork*100,2) as complete, --l.* l.sid, --l.opname, l.message, l.start_time, l.time_remaining/60 "minuts remaining", l.elapsed_seconds from gv$session_longops l where totalwork !=0 ) where complete < 100; The view is also usefull on specific operations such as Oracle Recovery Manager (RMAN) jobs monitoring, this query returns information about backup,restore and recovery. select sid, serial#,opname, context, sofar, totalwork, round(sofar/totalwork*100,2) "%_complet...
Post a Comment
Read more