Hans Forbrich wrote:
>
> Peter wrote:
>
>
>>Does a commit cause a checkpoint?
>>
>>A checkpoint causes the SCN to increment. A logswitch causes a
>>checkpoint and threrefore a SCN incremental change.
>>What I am confused about is whether a commit causes a checkpoint and
>>therefoe a SCN increment.
>>
>
>
> From the "Oracle9i Database Administrator's Guide, Release 2 (9.2), Part
> Number A96521-01" at
> http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96521/onlineredo.htm#ADMIN007
> in Chapter 7, "Managing the Online Redo Log", in section titled "Online
> Redo Log Contents",
>
> the second paragraph reads:
>
>
> Redo records are buffered in a circular fashion in the redo log buffer
> of the SGA (see "How Oracle Writes to the Online Redo Log") and are
> written to one of the online redo log files by the Oracle background
> process Log Writer (LGWR). Whenever a transaction is committed, LGWR
> writes the transaction's redo records from the redo log buffer of the
> SGA to an online redo log file, and a system change number (SCN) is
> assigned to identify the redo records for each committed transaction.
> Only when all redo records associated with a given transaction are
> safely on disk in the online logs is the user process notified that the
> transaction has been committed.
> <<<<<<<
>
> Please note the sentance starting with "Whenever a transaction is
> committed,"
>
> (I'm still wondering what is your documentation source - whatever it is
> seems to be leaving huge gaps in your understanding)
It takes time to understand how Oracle works. Please don't be so harsh.
Cheers,
Dave
>
> /Hans
>
>
>>Thanks
>
>
Received on Wed Jun 18 2003 - 19:57:11 CDT
