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Summary
ASSM (Automatic Segment Space Management) is a method used by Oracle to manage space inside data blocks. It eliminates the need to specify parameters like PCTUSED, Freelists and Freelist groups for objects created in the tablespace.
ASSM was first introduced with Oracle 9i. Starting with 10g Release 2, ASSM will be enabled by default when you create a new tablespace
Unfortunately ASSM has a lot of bugs!
For example when you try to make a Parallel Insert on a table stored in ASSM tablespace. After the insert issuing a commit will generate:
ORA-00607: Internal error occurred while making a change to a data block
ORA-00600: internal error code, arguments: [kddummy_blkchk], [25], [124266], [18038], [], [], [], []
Oracle remommends as a workaround to drop the table and recreate it (with export-import for example).
The best solution is to:
1. Create a new tablespace with Manual segment management.
CREATE TABLESPACE TS_MANUAL
DATAFILE '/app/orafata/ts1.dbf' SIZE 100M
EXTENT MANAGEMENT LOCAL
SEGMENT SPACE MANAGEMENT MANUAL
2. Move the table and indexes to the new tablespace (TS_MANUAL)
alter table X move tablespace TS_MANUAL;
The bug number is:
5386204 Block corruption / [kddummy_blkchk] after direct load of ASSM Segment
Other known ASSM issues:
ASSM Space Management (Bitmap Managed Segments)
3279497 Interupted (Ctrl-C) TRUNCATE can corrupt ASSM table
3610777 Excessive CPU from INDEX insert into ASSM index segment
4055634 TRUNCATE table has to much overhead when operating on empty segments
4188324 Wasted space possible in ASSM segments
4475314 DELETE then INSERT without commit on ASSM segment can be slow
4660718 Allow choice between space / performance for ASSM segments
4694312 Index inserts to ASSM segments can be slow
4887955 Unnecessary extent allocated in locally managed ASSM tablespace in RAC
5034679 Hang / errors making ASSM tablespace read only with concurrent DML
5349632 Poor performance for ASSM insert after large DELETE
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