• About Me

    Maxwell Miranda
    Oracle DBA Consultant.
  • Category

  • Archives

  • My Blog Calendar

    September 2009
    M T W T F S S
    « Aug   Oct »
  • RSS Oracle Feeds

    • 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 […]
    • Downgrade database from Oracle to Oracle using catdwgrd.sq
      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 […]
  • Advertisements

Difference between the Checkpoint and SCN

Checkpoint in database is used to reduce the amount of the time for recovery. It is a background process in oracle(CKPT), which cause DBWR to write all the data blocks that have been modified since the last checkpoint to the datafile.
Checkpoint is responsible for
->Signaling DBWn
->Updating datafile headers with checkpoint info. (i.e. SCN)
->Updating Control file with checkpoint info. (i.e. scn)

SCN is the ever increasing number to determine the age of database.
it’s System Change Number / System Commit Number…
It’s used to determine the consistency of database..
It’s stored at various places like control file, data files, redo log files.
If it doesn’t match, that means inconsistency..

So in short,
Checkpoint is the concept/background process while SCN is like serial number in our table..


One Response

  1. I want to know more about the role of SCN in recovery on oracle DATABASE.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: