Chapter 11. Managing Undo Data


Terms you'll need to understand:

  • Rollback

  • Undo

  • UNDO_MANAGEMENT

  • UNDO_TABLESPACE

  • UNDO_RETENTION

  • UNDO_SUPPRESS_ERRORS

  • V$UNDOSTAT

  • V$ROLLNAME

  • V$ROLLSTAT

  • V$TRANSACTION

  • V$SESSION

  • DBA_ROLLBACK_SEGS

  • CREATE UNDO TABLESPACE

Concepts you'll need to master:

  • Describe the purpose of undo data.

  • Implement automatic undo management.

  • Create and configure undo segments.

  • Obtain undo segment information from the data dictionary.

Historically, Oracle has used rollback segments to manage space dedicated to providing the ability to undo a transaction. This method (rollback segments) is now referred to as manual undo management mode. Manual undo management mode is still supported under all compatibility levels. You can still use this method when you are migrating to Oracle 9i to take advantage of some features or to be compliant, even if you are not yet ready to convert to automatic undo management mode (the new Oracle 9i method of automatically managing these segments). This chapter explains manual undo management and how it differs from automatic undo management.

The term undo has replaced what was known in previous versions of the database as rollback. This chapter covers automatic undo management and how it happens in the Oracle 9i instance and database.

In manual undo management, you create, allocate, and tune undo segments manually. This was the only option in previous releases of the database.



    Oracle 9i Fundamentals I Exam Cram 2
    Oracle 9i Fundamentals I Exam Cram 2
    ISBN: 0789732653
    EAN: 2147483647
    Year: 2004
    Pages: 244
    Authors: April Wells

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