DBACOCKPIT and parallel checkpoints

[lenm]

Dear Oracle Experts,

in transaction DB2 (DBACOCKPIT, etc.) under Performance - Additional Functions - Checkpoints, I can see a list of all Oracle Checkpoints that are in the alert log. Some are hightighted in yellow and from the documentation, this indicates parallel checkpoints. Can someone please explain what parallel Oracle checkpoints are and when and why they are necessary?

Thanks in advance and kind regards,

Michael

[Brindavan_M]

Hi Michael ,

The below information might be helpful to understand about check point in oracle.

The Checkpoint is a database event which synchronizes the modified data blocks to be written with datafiles on disk.

Types of checkpoints  in Oracle :

1) Full checkpoint

2) Thread checkpoint

3)File checkpoint

4) Parallel Query checkpoint

5) Object checkpoint

6) Log switch checkpoint

7) Incremental checkpoint

  PARALLEL QUERY CHECKPOINT

Parallel query often results in direct path reads (Full tablescan or index fast full scan). This means that blocks are read straight into the session’s PGA, bypassing the data cache; but that means if there are dirty buffers in the data cache, the session won’t see the most recent versions of the blocks unless they are copied to disk before the query starts – so parallel queries start with a checkpoint.

- Writes block images to the database for all dirty buffers belonging to objects accessed by the query from all instances.

- Statistics updated

  . DBWR checkpoints

  . DBWR checkpoint buffers written

- Caused by :

  . Parallel Query

  . Parallel Query component of Parallel DML (PDML) or Parallel DDL (PDDL)

- Mandatory for consistency

- Controlfile and datafile headers are updated

Thanks,

BM

[JamesZ]

Hi Michael,

Can you show me with the screenshot for "Parallel Oracle checkpoints"?

Yellow means checkpoints is a little bit frequent, at this stage checkpoint may decrease the performance.

Best regards,
James