||Oracle Tips by Burleson
Pitfalls to Avoid
So what about the pitfalls? What are they?
Honestly, it would be impossible to tell you all the possible points
of failure, but most will be resource-related, such as not enough
space. Letís look at a short list of possible points of failure.
* You donít have enough space in the SYSTEM
tablespace when using MIG or ODMA to migrate. The MIG or ODMA will
complain and abort if it doesnít have the space to create the new
dictionary tables. You will need at least two times the space your
current dictionary occupies as free space in the SYSTEM tablespace
to use MIG. You can run MIG in CHECK_ONLY mode to verify available
space (among other nice-to-knows). The Oracle binaries take up to
three times the size of Oracle7 binaries, so make sure there is
enough free space on the disk to accommodate them.
* If you are not using the export/import
method, both databases must have matching block sizes, and block
size must be at least 2048 bytes. Oracle will not accept a smaller
block size than 2048 bytes.
* If you are attempting to migrate from a
32-bit machine to a 64-bit machine using MIG, come on, get serious.
The only methods that work are export/import or sqlloader. I opt for
export/import in this situation.
* Going from one character set to another is
verboten (forbiddenÖdonít you learn a lot reading this stuff?). For
MIG, this isnít a problem, but for the other methods it could be. Be
sure to check your NLS parameters.
* Performing migration steps out of order.
Obviously, donít do this.
* Not fulfilling the prerequisites for
migration (see the first sections above).
* Allowing other users to access the
database during migration.
* Database must be at least 7.3.4. Iím not
kidding; it checks for this and errors out if it isnít.
* If you are re-creating control files in a
different location, be sure permissions are set properly.
* Be sure all tablespaces were either online
or in an offline normal or temporary status when the Oracle8
instance shut down. Be sure there is no outstanding undo in any of
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