Rebuilding indexes after importing...

Question

My coworker and I are discussing whether it is necessary, or advised, to rebuild indexes after an import of the schema.
My thinking is that the index data is put into fresh blocks thereby creating a very flat index tree without any fragmentation.
But my coworker suspects that perhaps the blocks are built exactly as they existed in the source database.
I could understand, perhaps, if the refresh were done by using RMAN which copies block by block, but even then I'm not sure.
Can you help us understand this please?
Thanks.
Ed

Answer 1

Hi,
Normally, the indexes are build and statistics upfated after the import automatically. You do not ned to generate the statistics after the import until unless you are running very old version of database.
Regards
[sfa-dev1:oracle:10.2.0] $ imp help=Y
Import: Release 10.2.0.4.0 - Production on Fri Nov 13 11:49:56 2009
Copyright (c) 1982, 2007, Oracle. All rights reserved.
You can let Import prompt you for parameters by entering the IMP
command followed by your username/password:
Example: IMP SCOTT/TIGER
Or, you can control how Import runs by entering the IMP command followed
by various arguments. To specify parameters, you use keywords:
Format: IMP KEYWORD=value or KEYWORD=(value1,value2,...,valueN)
Example: IMP SCOTT/TIGER IGNORE=Y TABLES=(EMP,DEPT) FULL=N
or TABLES=(T1:P1,T1:P2), if T1 is partitioned table
USERID must be the first parameter on the command line.
Keyword Description (Default) Keyword Description (Default)
USERID username/password FULL import entire file (N)
BUFFER size of data buffer FROMUSER list of owner usernames
FILE input files (EXPDAT.DMP) TOUSER list of usernames
SHOW just list file contents (N) TABLES list of table names
IGNORE ignore create errors (N) RECORDLENGTH length of IO record
GRANTS import grants (Y) INCTYPE incremental import type
INDEXES import indexes (Y) COMMIT commit array insert (N)
ROWS import data rows (Y) PARFILE parameter filename
LOG log file of screen output CONSTRAINTS import constraints (Y)
DESTROY overwrite tablespace data file (N)
INDEXFILE write table/index info to specified file
SKIP_UNUSABLE_INDEXES skip maintenance of unusable indexes (N)
FEEDBACK display progress every x rows(0)
TOID_NOVALIDATE skip validation of specified type ids
FILESIZE maximum size of each dump file
STATISTICS             import precomputed statistics (always) On 10gR2
Edited by: skvaish1 on Nov 13, 2009 11:50 AM