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    Maxwell Miranda
    Oracle DBA Consultant.
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    • Flashback database to date back and forth
      Code: --------- SELECT NAME, TIME FROM v$restore_point order by time; NAME TIME ---------------------------------------- ----------------------------------- RST_PNT_20180306_1135 06-MAR-18 AM *Got flashbacked to this 6th Mar* RST_PNT_20180308_0132 08-MAR-18 AM RST_PNT_20180315_0332 15-MAR-18 AM RST_PNT […]
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      Downgrade database from Oracle to Oracle Like to know if any one successfully downgraded the database from version Oracle 12cR2 ( Release 2) to Oracle 11g Release 2 ( using manual method of catdwgrd.sql. Please share your views and inputs as we are unable to downgrade it successfully. Refereed the https://docs.oracle.com/en/databa […]
    • New user in oracle having access to all tables
      Hi, I have created a new user in oracle database as follows create new user u1 identified by u1; grant create session to u1; when I login with new user ,it has access to all tables in other schema except system and sys tables. i want to create a user who does not have access to any table on any schema. how it can be achieved? Thanks
    • Auditing userid creation, deletion and changes to roles granted.
      Is there an oracle auditing option to audit userid creation, deletion and changes made to the userid (system/object privileges granted or revoked)?
    • ORACLE SQL - Adding Results from Multiple Select Statements
      I apologize if this question is not in the correct area. I have eight select statements, each to get the sum of particular information. These are not simple queries, so I will not include them here. I have made up a simpler version (based on some code I found in a forum) as shown below. So, I have eight sums. I need a ninth sum that is the total of all eight […]
    • Cannot change undo_tablespace parameter in RAC node
      Hi, I am trying to change the undo tablespace in DB instance, unsuccessfully. Approach 1: SQL> show parameter undo NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ temp_undo_enabled boolean FALSE undo_management string AUTO undo_retention integer 900 undo_tablespace string *UNDOTBS2* SQL> SQL> ALTER SYS […]
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Optimal undo sizing

Note: Only run this query after the database has
been running for a significant/representative
period of time.

Note2: This script is for when space is no issue and
you want to determine the optimal size based
on database activity and your desired
undo retention time.

Note3: If “NEEDED UNDO SIZE” is less than “ACTUAL UNDO SIZE”
then this is generally and indication of wasted space.

set linesize 150
column “UNDO RETENTION (Secs)” format a25

d.undo_size/(1024*1024) “ACTUAL UNDO SIZE (MEGS)”,
substr(e.value,1,25) “UNDO RETENTION (Secs)”,
(to_number(e.value) * to_number(f.value) * g.undo_block_per_sec) / (1024*1024) “NEEDED UNDO SIZE (MEGS)”
sum(a.bytes) undo_size
v$datafile a,
v$tablespace b,
dba_tablespaces c
c.contents = ‘UNDO’ and
c.status = ‘ONLINE’ and
b.name = c.tablespace_name and
a.ts# = b.ts#
) d,
v$parameter e,
v$parameter f,
max(undoblks/((end_time-begin_time)*3600*24)) undo_block_per_sec
) g
e.name = ‘undo_retention’ and
f.name = ‘db_block_size’;


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