I just stumbled upon this bug reference on My Oracle Support:

Bug 13262857  Enh: provide some control over DBMS_STATS index clustering factor computation

This enhancement was long due. Previously, when computing the clustering factor during gathering statistics, the value was incremented, whenever the row was not found in the same block as the previous row. Now, it is finally possible to determine how many blocks should be considered when computing clustering factor. The patch delivers an improved DBMS_STATS package body that can be used to set preferences with value TABLE_CACHED_BLOCKS.

The flaw in the over-simplistic and pessimistic original computation was (more...)

Recently, i was troubleshooting a datapump export duration problem. Over the period of 18 months, the duration of a multi-table export increased dramatically. A quick analysis showed that the export duration was mainly dependent on one big table. This 50 GB table with no BLOB/CLOB/LONG datatypes took more than 4 hours on a modern system wheras it should not take more than 10 – 15 minutes. The system was performing ONLY single-block I/O requests (db file sequential read). I found this strange and started investigating.

Beginning with 11g, you can enable sql_trace (10046) for datapump with the new syntax:

ALTER  (more...)

I would like to point your attention to a bug in RAC 11.2.0.3. The bug leads to instance crashes during Dynamic Remastering. As of June 1st, there is no patch publicly available. The workaround seems to be to set:

_gc_read_mostly_locking=false

So, if you are thinking about upgrading your RAC to 11.2.0.3, maybe you should wait just a little bit longer…

More details are in MOS: Bug 13397104: INSTANCE CRASH WITH ORA-600 [KJBLPKEYDRMQSCCHK:PKEY]

Update 12.06.2012: Patch 13397104 is now available in MOS for 11.2.0.3.

Oracle yesterday announced certification of RHEL6 / OEL6 with Oracle Database 11gR2 and Oracle Fusion Middleware 11.1.

Moreover, Oracle will from now on provide errata packages for free. Until now, they could only be obtained with a valid ULN support contract. I think this will be a big plus for Oracle Linux in competition with Red Hat Enterprise Linux.

I wonder how long it will take before they ship Exadata and Oracle Database Appliance (ODA) with Unbreakable Kernel.

Reference: http://www.oracle.com/us/corporate/press/1563775

Gone are the day when cleartext passwords had to be stored in scripts for Oracle database access. The solution to this requirement is “Oracle Secure External Password Store (SEPS)”. This article will give a short introduction and a practical example of the solution.

Key facts:

Installation

• Oracle Client: Unix-Account, who wishes to connect to the database without providing a password needs to (more...)

I just saw MOS Note

ORA-4031 After Upgrade From 11.2.0.1 To 11.2.0.3 With Leak in ‘KTC latch subh’ Subheaps [ID 1398984.1]

giving very little information about this bug. At the time of this writing, there is no patch available but I expect it to be in a few days. I have checked some 11.2.0.3 instances and found only one with > 60 MB for this subheap.

In case you have not heard all the buzz about the Oracle SCN flaw, which was published by Infoworld after the release of January CPU, I summarize the essentials.

• There is a risk that the SCN reaches it´s maximum value and this could lead to an outage of the database.
• There is a bug in “ALTER DATABASE BEGIN BACKUP”, which increases the SCN dramatically. (Bug 12371955 – fixed in 11.2.0.2.4 and others)
• When you query a remote database via database link from a database with elevated SCN, the remote SCN gets increased to the higher value (more...)

At one of my customers, we wondered about some entries in v$datafile.unrecoverable_change# for the most critical tablespace of the application. Certainly no application components were allowed to perform nologging operations for segments inside this tablespace and yet there was evidence that “something” was done with nologging.

• The unrecoverable_time was shortly after 10 pm
• The ASH data covering this time period showed activity by DBMS_SCHEDULER and Autotask Jobs.
• An internal DDL log table showed the following operations:

CREATE TABLE "MYOWNER".DBMS_TABCOMP_TEMP_UNCMP
tablespace "DAT_MYOWNER" nologging
AS
SELECT /*+ FULL("MYOWNER"."MYTAB") */ *  FROM "MYOWNER"."MYTAB"  sample block( 3.55)  (more...)

From time to time we hit Errors like ORA-600 or ORA-7445, which are triggered by specific SQL statements. For these cases, Oracle developed the SQL Repair Advisor. This is a short demonstration of utilizing the SQL Repair Advisor to avoid ORA-7445 caused by a SQL statement.

SQL and Error:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

SELECT
EXTRACT(YEAR FROM date_new) jahr,
EXTRACT(MONTH FROM date_new) monat,
COUNT(DISTINCT TRUNC (more...)