Multiplex online Redo Logfile

It is important to have multiple (at list two) copy of each online redo logfile. To avoid the disaster of disk failure, it is recommended to place each member of a specific online redo logfile group in different disk.

To view to current online redo logfile group members

SELECT GROUP#,STATUS,MEMBER FROM V$LOGFILES;

Suppose we have disk01 (mount point /u01 ) that contains current online redolog files .To add member in redo logfile group 1,2 and 3 in disk02 ( mount point /u02 )

ALTER DATABASE ADD LOGFILE MEMBER '/u02/redo01.log' TO GROUP 1;
ALTER DATABASE ADD LOGFILE MEMBER '/u02/redo02.log' TO GROUP 2;
ALTER DATABASE ADD LOGFILE MEMBER '/u02/redo03.log' TO GROUP 3;

Track Database Growth

Some time it become very important to monitor your database growth specially in test database machines. Usually these machines have very limited disk space.
Thus, tracking the consumption of disk space is one of the frequent tasks in administrative checklist. Here is a SQL script that gives you the current size of database and average disk space consumed in each day.


SELECT b.tsname tablespace_name
, MAX(b.used_size_mb) cur_used_size_mb
, round(AVG(inc_used_size_mb),2)avg_increas_mb
FROM (
SELECT a.days,a.tsname
, used_size_mb
, used_size_mb - LAG (used_size_mb,1) OVER ( PARTITION BY a.tsname ORDER BY a.tsname,a.days) inc_used_size_mb
FROM (
SELECT TO_CHAR(sp.begin_interval_time,'MM-DD-YYYY') days
,ts.tsname
,MAX(round((tsu.tablespace_usedsize* dt.block_size )/(1024*1024),2)) used_size_mb
FROM DBA_HIST_TBSPC_SPACE_USAGE tsu
, DBA_HIST_TABLESPACE_STAT ts
,DBA_HIST_SNAPSHOT sp, DBA_TABLESPACES dt
WHERE tsu.tablespace_id= ts.ts# AND tsu.snap_id = sp.snap_id
AND ts.tsname = dt.tablespace_name AND sp.begin_interval_time > sysdate-7
GROUP BY TO_CHAR(sp.begin_interval_time,'MM-DD-YYYY'), ts.tsname
ORDER BY ts.tsname, days
) a
) b GROUP BY b.tsname ORDER BY b.tsname;