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Thread: Export

  1. #1
    Join Date
    Mar 2001
    Posts
    54
    I have one basic doubt in Export Method.

    We are Exporting our database by direct method.My senoir DBA had written the script.He is using buffer= parameter.I studied some where Direct export will use recordlength rather than buffer.

    Which one is correct?

    Kindly advice me
    Jeyaseelan

  2. #2
    Join Date
    Feb 2001
    Location
    Bombay,India
    Posts
    530
    Hi,
    The BUFFER parameter applies ONLY to conventional path Export. It has no effect on a direct path Export.
    This BUFFER parameter specifies the size (in bytes) of the buffer used to fetch rows. It determines the maximum number of rows in an array, fetched by Export.
    For direct path Export, use the RECORDLENGTH parameter to specify the size of the buffer that Export uses for writing to the export file.


    In case of any help please be free to ask me at rohitsn@altavista.com

    Regards,
    ROhit Nirkhe,Oracle DBA,OCP 8i
    rohitsn@altavista.com

  3. #3
    Join Date
    Aug 2001
    Posts
    111
    The doco explains this in this note

    Note: The BUFFER parameter applies only to conventional path Export. It has no effect on a direct path Export.

    Here a direct paste from 8.1.7 doco concerning

    Record length:
    Specifies the length, in bytes, of the file record. The RECORDLENGTH parameter is necessary when you must transfer the export file to another operating system that uses a different default value.

    If you do not define this parameter, it defaults to your platform-dependent value for BUFSIZ. For more information about the BUFSIZ default value, see your operating system-specific documentation.

    You can set RECORDLENGTH to any value equal to or greater than your system's BUFSIZ. (The highest value is 64KB.) Changing the RECORDLENGTH parameter affects only the size of data that accumulates before writing to the disk. It does not affect the operating system file block size.

    You can use this parameter to specify the size of the Export I/O buffer.

    I would test to see if there is any benefit increasing the RECORD LENGTH above the system maximum.
    If you have mutliple CPUs and disk array, spliting the export into chunks of tables will be faster (to a point) as you achieve some parallelism.

    Have Fun
    Performance... Push the envelope!

  4. #4
    Join Date
    Mar 2001
    Posts
    54
    Hi rohit,

    Thankx for your suggestion.

    That database size is 10GB and we are taking daily full export direct method backup.It takes around 4 Hours to complete the export.We want to reduce the time.

    As i mentioned earlier ,my senior DBA had writted that script as

    exp full=y direct=y buffer=20000000......

    Now i want to change the scripts as

    exp full=y direct=y recordlength=20000000...

    Can i put the same buffer size for recordlength ?

    regards
    Jeyaseelan

  5. #5
    Join Date
    Mar 2001
    Posts
    188

    Thumbs up

    hey jeyaseelan,
    i have taken a lot of time in the last day with this issue.
    I think there is a better solution.
    If you have time than read this:

    Look for the parameter INCTYPE is is a good solution.
    Here is an example for one week.
    You take only once a week a full export with the following parameters full=y inctype=complete
    Then the next two day you make an incremental export with the following parameters full=y inctype=incremental.
    Then you make a cumulative export. This makes you with the following parameters full=y inctype=cumulative and the next 3 day you make only an incremental export with the parameters full=y inctype=incremntal.

    The advantage of this strategy is that the time for the cumulative and incremental export are shorter. And the full export you can make on the weekend when nobody the db needs. So you have in the buisnesshour good performace.

    I hope i ould help you.
    If you have more question please mail me to the mail-address in the bottom.

    So long
    Thomas Schmidt
    Best Regards
    Thomas Schmidt

    Thomas_Schmidt@eplus-online.de
    If you have no aims, you will never reach a goal !!!

  6. #6
    Join Date
    Jun 2000
    Location
    Madrid, Spain
    Posts
    7,447
    i have never seen anyone using incremental export as backup strategy and Oracle is planning to get rid of this feature

    why do you export everyday?

    dont you have your database in archive log mode? if you do just export the important tables everyday not the whole database and export full once a week

  7. #7
    Join Date
    Mar 2001
    Posts
    54
    Last one week i struggled to take a full backup of my database,atlast i succedded with impst instead of import.
    Itz very very speed.Excellent.

    It may be usefull for the people who are facing the same type
    of problem.


    Thanx
    Jeyaseelan

  8. #8
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
    Posts
    3,938
    i have never seen anyone using incremental export as backup strategy and Oracle is planning to get rid of this feature
    I have. But it makes sence in megabases.

    why do you export everyday?
    This question was not meant for me but I will also answer it.
    I have the database in archive log mode. I backup with RMAN every day and export every day. Backup of the backup :-) We are an investment bank, every row in every table is crutial. We cannot afford to loose data. Not a single transaction. If something goes wrong with the backups I have at least last night's dumps.


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