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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Extent size of locally managed tablespaces
Hi Chuck,
The bitmap for LMT's need only 64K.
When you create the datafile, make sure you add 64K to the datafile size and
then it will grab the 1st extent for the bitmap.
For eg:
if you have a tablespace that is 500M and you want 50M extents uniform size,
then create the tablespace with a datafile size of 500*1024 = 512000K + 64K
= 512064K.
If you create it as 512000K then you get only 9 extents of 50M = 450M and one extent of 50M is used for the bitmap. If you create it with 512064K then you get ten extents of 50M each at 512000K and 64K is used for the bitmap.
You can check in dba_datafiles "user_bytes" gives you the bytes that are allowed to be used and "bytes" which is the allocated bytes. In the case of the datafile being 512000K you will see 450M in user_bytes and 500M in bytes. If you allocate 512064K you will see 500M in user_bytes and 512064K in allocated bytes.
The bitmap basically needs 64K in each datafile to track the extents and keep track of the allocation and deallocation.
Please let me know if you need more information
Regards,
Madhavan
IBM Corporation
>From: Chuck Hamilton <chuck_hamilton_at_yahoo.com>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: Extent size of locally managed tablespaces
>Date: Thu, 20 Jul 2000 07:42:39 -0800
>
>
>I want to set up a locally managed tablespace that allocates data in 50m
>chunks. When I create it with "extent management local uniform size 50m"
>however, the first extent is allocated (for the bitmap?) at 50m. That's a
>lot of space to waste on a bitmap. Is there some way to reduce the bitmap
>size and still keep the extents large?
>
>
>
>
>
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