Database - 68. page

ora 10g 10201

BUG1：shutdown immediate 时系统hung住，经metalink查询：

Verify that temporary segments are decreasing
———————————————
To verify that the temporary segments are decreasing have an active session
available in Server Manager or SQLPLUS during the SHUTDOWN IMMEDIATE. Issue the following
query to ensure the database is not hanging, but is actually perform extent
cleanup:

SVRMGR/SQL> select count(block#) from fet$;
COUNT(BLOC
———-
7

SVRMGR/SQL> select count(block#) from uet$;
COUNT(BLOC
———-
402

After some time has elapsed, reissue the query and see that the values for fet$
have increased while the values or uet$ have decreased:

SVRMGR/SQL> select count(block#) from fet$;
COUNT(BLOC
———-
10

SVRMGR/SQL> select count(block#) from uet$;
COUNT(BLOC
———-
399

During shutdown the SMON process is cleaning up extents and updating the data
dictionary tables with the marked free extents. As the extents are marked as
freed, they are removed from the table for used extents, UET$ and placed on the
table for free extents, FET$.

How to Avoid creating many Temporary Extents
——————————————–
Once the database has shutdown cleanly, to avoid creating many temporary
extents change the initial and next extent sizes on temporary tablespaces
to a more appropriate size:

ALTER TABLESPACE DEFAULT STORAGE (INITIAL M/K NEXT M/K);

Note: If the temporary tablespace is of type TEMPORARY, then this change
will only affect temporary segments created after issuing the above
command. Any existing temporary segments already in the TEMPORARY tablespace
will not be affected till the instance is restarted. On shutdown, existing
temporary segments are dropped. If the TEMPORARY TABLESPACE is of type
PERMANENT, then cleanup is performed by SMON after completion of the process
using it.

Increasing the initial and next extent size will decrease the number of extents
that are allocated to temporary segments. Since there are fewer extents to
deallocate, the database should shutdown more speedily.

Take the following scenario:

A database was subject to large sorts with the following sort parameter in
the “init.ora” file:

– sort_area_size=1000000

The temporary tablespaces for this database were all created with initial and
next extents sized at 50k and the total database size was about 300mb.

Database sorts will utilize memory as much as possible based on the “init.ora”
parameter “sort_area_size”. Once this memory-based sort area is filled, the
database will utilize the temporary table space associated with the database
user to complete the sort operation. During a shutdown normal, the database
will attempt to clean up the temporary tablespaces.

If a small extent size is used, then a large number of extents will be created
for a large sort. The cleanup of the temporary tablespace takes much longer
with a large number of extents.

Note:
=====
You have to do a shutdown abort and then bring the database
back up to run the suggested queries.

For other reasons for slow/hung shutdown see also these notes:

Note 375935.1 – What To Do and Not To Do When ‘shutdown immediate’ Hangs
Note 428688.1 – Bug:5057695: Shutdown Immediate Very Slow To Close Database.

References:
===========Note:61997.1 SMON – Temporary Segment Cleanup and Free Space Coalescing

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