RMAN: Restore missing archivelogs

SQL> select sequence#, applied, to_char(first_time,’dd-mm-yyyy hh24:mi:ss’) first_time
from v$archived_log
order by sequence#;

SQL> select process,sequence#,status from v$managed_standby;
PROCESS STATUS SEQUENCE# FIRST_TIME
------------ ---------- -------------------
ARCH CONNECTED 0
ARCH CONNECTED 0
MRP0 WAIT_FOR_GAP 7279
RFS WRITING 7299

WAIT_FOR_GAP means thare are missing archivelogs. You need to recover them.


We first identify whose are missing:

[oracle@ora-test ~]$ sqlplus / as sysdba
SQL> select * from v$archive_gap;


   THREAD# LOW_SEQUENCE# HIGH_SEQUENCE#

---------- ------------- --------------

         1          7279           7286

We then use RMAN to recover them:

[oracle@ora-stb ~]$ rman target / catalog rman/password@rman_repo
RMAN> restore archivelog sequence between 7279 and 7286;

You can now check

[oracle@ora-stb ~]$ ls –l /archivelog_folder/arch_72[7-8]*

DBMS_LOGMNR, or "How to see what's in the redo logs"

Contents:
1 Database-Level Supplemental Logging
2 Redo Log File Options
3 Example of Querying V$LOGMNR_CONTENTS
4 End the LogMiner Session

Database-Level Supplemental Logging:

ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;

Redo Log File Options

Here you will tell you LOGMNR whate logfiles to look into. It can be done:

Automatically. Just define the time range you want to observe and start logmnr.

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';

EXECUTE DBMS_LOGMNR.START_LOGMNR( STARTTIME => '01-Jan-2003 08:30:00', ENDTIME => '01-Jan-2003 08:45:00', OPTIONS =>
DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG + DBMS_LOGMNR.CONTINUOUS_MINE);

Manually. You need to manually add every logfile you're interested in and then start logmnr.

EXECUTE DBMS_LOGMNR.ADD_LOGFILE( LOGFILENAME => '/oracle/logs/log1.f', OPTIONS => DBMS_LOGMNR.NEW);

EXECUTE DBMS_LOGMNR.ADD_LOGFILE( LOGFILENAME => '/oracle/logs/log.f', OPTIONS => DBMS_LOGMNR.ADDFILE);

EXECUTE DBMS_LOGMNR.START_LOGMNR(OPTIONS => DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG);

Example of Querying V$LOGMNR_CONTENTS

SELECT OPERATION, SQL_REDO, SQL_UNDO
  FROM V$LOGMNR_CONTENTS
  WHERE SEG_OWNER = 'OE' AND SEG_NAME = 'ORDERS' AND
  OPERATION = 'DELETE' AND USERNAME = 'RON';

End the LogMiner Session

EXECUTE DBMS_LOGMNR.END_LOGMNR;

Note: Everything is related to your session, so if you got disconnected, start again

Source: http://download.oracle.com/docs/cd/B28359_01/server.111/b28319/logminer.htm#i1015913

Oracle: Archivelog activity

This will give you the number of logfile switch per hour. You will then be able to see the pics of activity (ie. data that has to be written) in your redo log.
It's similar than checking the number of "archivelog current", the only difference is with the writting mode in the logs. archivelog current is synchronous, switch logfile is asynchronous.

Date format: DD/MM/YYYY

SELECT
    SUBSTR(TO_CHAR(first_time, 'DD/MM/RR HH:MI:SS'),1,5)                          DAY
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'00',1,0)) H00
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'01',1,0)) H01
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'02',1,0)) H02
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'03',1,0)) H03
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'04',1,0)) H04
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'05',1,0)) H05
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'06',1,0)) H06
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'07',1,0)) H07
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'08',1,0)) H08
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'09',1,0)) H09
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'10',1,0)) H10
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'11',1,0)) H11
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'12',1,0)) H12
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'13',1,0)) H13
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'14',1,0)) H14
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'15',1,0)) H15
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'16',1,0)) H16
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'17',1,0)) H17
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'18',1,0)) H18
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'19',1,0)) H19
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'20',1,0)) H20
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'21',1,0)) H21
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'22',1,0)) H22
  , SUM(DECODE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH24:MI:SS'),10,2),'23',1,0)) H23
  , COUNT(*)                                                                      TOTAL
FROM
  v$log_history  a
WHERE
    TO_DATE(SUBSTR(TO_CHAR(first_time, 'MM/DD/RR HH:MI:SS'), 1,8), 'MM/DD/RR') >=  TO_DATE('&startDate', 'DD/MM/YYYY')
AND
    TO_DATE(substr(TO_CHAR(first_time, 'MM/DD/RR HH:MI:SS'), 1,8), 'MM/DD/RR')   <=   TO_DATE('&endDate', 'DD/MM/YYYY')

GROUP BY SUBSTR(TO_CHAR(first_time, 'DD/MM/RR HH:MI:SS'),1,5)

You will have a result similar to this:

It will help you to find the times where your db has the most activity in data writing.