Is CREATE INDEX smart-scanable ?

The answer is YES !
Look:

set timing on

CREATE UNIQUE INDEX "DW_STG"."UK#CALLS_00" ON "DW_STG"."CALLS_00" ("CALL_ID")   PCTFREE 0 INITRANS 24 MAXTRANS 255 PARALLEL 64  ;

You can see the column "Cell Offloading" = 95%

Tables will inherit HCC compression from Tablespace

We are on the Exadata.
The idea: to create the tablespace with HCC and move tables there.
Will tables be HCC-compressed ? Will tables inherit the COMPRESS FOR from the tablespace ?

Today i did the test and answer is YES !

Test env: we have the table BILLS in the non-HCC tablespace.
I created the new tablespace:

SQL> create bigfile tablespace HCC blocksize 8k datafile '+DATAC1'
size 1344m autoextend on next 1344m maxsize unlimited
default COMPRESS FOR QUERY HIGH
extent management local uniform size 4m
segment space management auto;

Tablespace created.

SQL> create table BILLS_HCC tablespace HCC as select * from BILLS;

Table created.

SQL> select segment_name, bytes from dba_segments where segment_name like 'BILLS%';

SEGMENT_NAME             BYTES
------------ -----------------
BILLS              27313307648
BILLS_HCC           6954156032


SQL> select 27313307648/6954156032 from dual;

27313307648/6954156032
----------------------
  3.927623642943305187

SQL> select table_name, compression,compress_for from dba_tables where table_name like 'BILLS%';

TABLE_NAME       COMPRESS COMPRESS_FOR
---------------- -------- ------------
BILLS_HCC        ENABLED  QUERY HIGH
BILLS            DISABLED

SQL> set timing on
SQL> select count(*) from BILLS;

            COUNT(*)
--------------------
           146432303

Elapsed: 00:00:02.83
SQL> select count(*) from BILLS_HCC;

            COUNT(*)
--------------------
           146432303

Elapsed: 00:00:02.65

Patchmgr hungs in the process of patching IB switches

As you know, the January 2014 Quarterly Full Stack Patch (QFSP) for Exadata contain new IB switches version - 2.1.3-4.
In many cases (my experience - 4 switches of 6) the command hungs:
./patchmgr -ibswitches -upgrade

It nothing do and wait something. We waited 1 hour and press Ctrl+C.
 
The SOLUTION is:

When you connect to Unix server the ssh daemon running on this server get your IP and try to resolve your IP into the name.
Such behavior is controlled by parameter UseDNS in /etc/ssh/sshd_config file.
By default the line look like:
#UseDNS=yes

Remove the # and change it to "no" :
UseDNS=no

And run patchmgr again !

Is it acceptable / supported to install additional or 3rd party software on Exadata machines and how to check for conflicts?

The interesting note appeared on the MOS:

Is it acceptable / supported to install additional or 3rd party software on Exadata machines and how to check for conflicts? 
(Doc ID 1541428.1)

 In short:


Answer is a qualified yes (Customers can add software ONLY to the DB Nodes, never to the storage cells).
Items to consider before installing additional RPMS:
1) Customer installed software must not update any Exadata provided packages.
2) Customer is fully responsible for the additional software.
3) Future Exadata Software updates may remove customer installed packages or the upgrades may fail due to customer installed packages.
4) If a customer installed package is removed as part of an Exadata Software update, the customer is responsible for re-verifying the package and re-installing if needed.

 

System performance utilities show wrong CPU load on Intel processosrs when HyperThreading is enables

The interesting information is published in the

http://www.oracle.com/technetwork/database/availability/exadata-health-resource-usage-2021227.pdf

 
pages 28-29:

"Compute node CPU utilization can be measured through many different tools – top, AWR, iostat, vmstat, etc. and they all give the same number, and % CPU utilization typically averaged over a set period of time. Choose whichever tool is most convenient, but allow for Intel CPU hyper-threading.

The Intel CPUs used in all Exadata models run with two threads per CPU core. This helps to boost overall performance, but the second thread is not as powerful as the first. The operating system assumes that all threads are equal thus overstates the available CPU capacity by the operating system. We need to allow for this. Here is an approximate rule of thumb that can be used to estimate actual CPU utilization, but note that this can vary with different workloads:

∙ For CPU utilization less than 50%, multiply by 1.7.

∙ For CPU utilization over 50%, assume 85% plus (util-50%)* 0.3.

Here is a table that summarizes the effect: Measured Utilization	Actual Utilization
10%	17%
20%	34%
30%	51%
40%	68%
50%	85%
60%	88%
70%	91%
80%	94%
90%	97%
100%	100%

 "

This information is applicable to all x86 abd x86-64 servers with HyperThreading enabled.

Enabling HT causes system statistics tools - vmstat, sar - show incorrect CPU load,
and Oracle performance tools - AWR, ASH - also show and store incorrect CPU load statistics.

Be careful !