Oracle SQL to return a alphabetical subset

Yes, I know, I've been waaay bad at blogging lately. Been busy working on new projects at work, upgrading applications to Java1.5 containers (Websphere 6.1, Weblogic 9.2 etc). On the fun side we've got an Azul Java-acceleration box, that really needs a couple of blog entries!

Anyway, got asked if there was a way to return a resultset of data based on the leading character, the use case was to ignore all strings starting with a,b, or d and return e to z.

Fairly straight forward but a good SQL to have.
I simply grab the first character in the varchar and compare it's ASCII value to the ASCII value D.

SQL> select * from t;

A
----------
Atest
Btest
Etest
Htest
Wtest
Dtest
dtest
SQL> with data as (
  2  select ascii(upper(substr(a,1,1))) a_val,a from t
  3  )
  4  select * from data where a_val not between ascii('A') and ascii('D') order by a
  5  /

     A_VAL A
---------- ----------
        69 Etest
        72 Htest
        87 Wtest
SQL>

Oracle 11g: Archive log alert log output

Starting with Oracle 11g the archivelog process is no longer logged to the alert log by default. For good and bad in my opinion, nice to get rid of the log entries on smaller databases but it can be quite useful to see the details on larger systems with multiple log destinations.

The log level is simply a database parameter and can easily be changed, look at this page to figure out what level you want. I figured 79 would be a good starting point (64+8+4+2+1). Databases running dataguard should probably have 207 (add 128) to include FAL service details.

How to set the trace level:

[oracle@vm-rac1 ~]$ rsqlplus "/ as sysdba"

SQL*Plus: Release 11.1.0.6.0 - Production on Sun Aug 19 02:35:23 2007

Copyright (c) 1982, 2007, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> show parameter log_archive_trace

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
log_archive_trace                    integer     0
SQL> alter system set log_archive_trace=79;

System altered.

SQL> alter system switch logfile;

System altered.

SQL> Disconnected from Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@vm-rac1 ~]$ talert # my shell alias to tail the current alert log
  Current log# 1 seq# 7 mem# 0: /u01/app/oracle/oradata/test11g/redo01.log
Sun Aug 19 02:03:14 2007
ARC3: Evaluating archive   log 3 thread 1 sequence 6
ARC3: Beginning to archive thread 1 sequence 6 (627362-628594) (test11g)
ARC3: Creating local archive destination LOG_ARCHIVE_DEST_10: 
'/u01/app/oracle/flash_recovery_area/TEST11G/archivelog/2007_08_19/o1_mf_1_6_%u_.arc' (thread 1 sequence 6)
 (test11g)
ARC3: Creating local archive destination LOG_ARCHIVE_DEST_1: 
'/u01/app/oracle/11.1.0/db_1/dbs/arch1_6_630935902.dbf' (thread 1 sequence 6)
 (test11g)
ARC3: Closing local archive destination LOG_ARCHIVE_DEST_10: 
'/u01/app/oracle/flash_recovery_area/TEST11G/archivelog/2007_08_19/o1_mf_1_6_3dh5pld1_.arc'
 (test11g)
Committing creation of archivelog 
'/u01/app/oracle/flash_recovery_area/TEST11G/archivelog/2007_08_19/o1_mf_1_6_3dh5pld1_.arc'
ARC3: Closing local archive destination LOG_ARCHIVE_DEST_1: 
'/u01/app/oracle/11.1.0/db_1/dbs/arch1_6_630935902.dbf'
 (test11g)
Committing creation of archivelog '/u01/app/oracle/11.1.0/db_1/dbs/arch1_6_630935902.dbf'
ARC3: Completed archiving thread 1 sequence 6 (627362-628594) (test11g)

Read details about the log trace level here and general alert log related stuff here.

Oracle 11g: basic rundown

Ok, so 11g has been out some time but I've been to busy to really dig in to it until now. 11g is probably the first release that doesn't really many new features; no, before you send me angry e-mails hear me out :)
Take a look at the new features list. What do most of these features do? Easy, they just make the most out of the fairly old but totally outstanding REDO and UNDO management in Oracle. Why not use what we already got? Ok, some things are totally new features like the improved partitioning and new data types for the medical and life-sciences industry.

Partitioning and compression
The coolest things in 11g is probably the VLDB features for partitioning and compressions, can really reduce storage costs (at the same time as storage costs are plummeting with the competition from iSCSI). It is now possible to create "automatic" partitions, i.e. instead of adding a partition every month with DDL when doing a bulk load Oracle can automatically partition the table as per predefined rules. Pretty cool and saves a lot of time.

Direct NFS
Another pretty cool feature, at least for me as I'm using a lot of Netapp NFS storage, is the Direct NFS client in Oracle (Linux). Switch to the direct NFS lib and Oracle will do NFS ops outside the Linux kernel, which removes the NFS caching layer and kernel block device mapping etc. Gives a quite massive performance increase on some workloads. This is what I'm playing most with at the moment.

Data Guard
Lots of new cool stuff for Data Guard. Most significantly is probably the fact that you can have an open standby, available for real-time queries such as reporting applications and other read only operations. In fact, you can even open a Data Guard instance in read-write mode and mess about with it and later just flashback to a SCN where the db was in sync with the Data Guard master db and just roll forward to the current SCN using the normal FAL services. How sweet isn't that for DR testing and schema change testing. DR testing during live operations, that's a couple of late nights saved.
Other new data guard features include redo shipping compression, the normal improvements to the DG broker, sqlplus manageability etc.


Workload replay
Another thing that is really useful for deployment testing and change control is the database replay feature, one can "record" all transactions over a period of time and replay them after a change has happened to ensure performance and functionality has not degraded.


Improved ASM features.
You can now bring online a replaced drive and new writes will go directly to the drive while Oracle sync data from a redundant mirror in the background. Reduces resync time quite a fair bit.

PL/SQL
Couple of improvements to plsql;
Use of sequences in declares.
Real compound triggers.

New data types
Not really my thing but probably useful for a lot of people.
Spatial and multimedia support for medical imaging, life-sciences and other fairly odd things. :) Docs here.

A couple of minor things have changed as well, the alert log lives in a new place (with it's buddies in the new diag system), the logging levels in the alert log can now be adjusted as well (got a blog entry about that in a couple of days).

Lots of fun things to play with and to blog about.

Ah, almost forgot. Larry pulled a version hack on us again. As some of you may now there was never an Oracle Version 1 release, the first version was called 2 since Larry Ellison didn't think anyone would buy version 1. The first (public) 11g release is 11.1.0.6

Oracle Database 11g available for download

Well, it's about time. Oracle finally made 11g available for download. Only 32-bit Linux so far though and I have a feeling we'll have to wait a while for most other platforms (possibly a 64-bit Linux download soon).

Download it here.

Lots of new cool stuff to blog about, I'm away on holiday for a week but my recently upgraded lab machines at home are sitting there waiting. Fun times when I get home.

Limit user sessions in Oracle

Developers sometimes enjoy configuring their JDBC datasources after their own likings, testing a performance issue by having a gazzillion threads to the database "just in case we need them".
Well in my opinion, if you need what is obviously too many threads, then there is a coding issue.
So to make people think twice before flooding a service with connections I've started limiting the number of sessions they are allowed to have.
Easy as always to do in Oracle. First we allow resource limits by setting the resource_limit to true, then we simply create a profile and assign that to the user. The profile can set the limit of how many session a user is allowed to have.

A little demonstration;

oracle@htpc:~$ rsqlplus "/ as sysdba"

SQL*Plus: Release 10.2.0.1.0 - Production on Mon Jul 30 21:56:12 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL> show parameter resource_limit

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
resource_limit                       boolean     FALSE
SQL> alter system set RESOURCE_LIMIT=true scope=both;

System altered.

SQL> create profile sesslimit limit sessions_per_user 2;

Profile created.

SQL> create user fish identified by fish123
  2  default tablespace data profile sesslimit;

User created.

SQL> grant create session to fish;

Grant succeeded.

SQL> connect fish/fish123
Connected.
SQL> disconnect
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
-- I'll start two sessions in another terminal.
SQL> connect fish/fish123
ERROR:
ORA-02391: exceeded simultaneous SESSIONS_PER_USER limit


SQL>

Using SERVICE_NAMES in Oracle

The use of "SERVICE_NAMES" in Oracle is quite an old and probably well known feature but perhaps not everyone is familiar with it yet.
Got asked today about a recovery scenario where the administrator had a failed instance (broken data files, no logs, no backups, just a nightly exp), a new database was created with 'dbca', but with a new name to test importing the exp file.
All worked fine, but there was a problem with the database name. The application had the service name set in a number of config files and there was also a number of ETL scripts with service names hardcoded. The thinking at the time was to delete the old instance, remove all traces of it (oratab etc.) and then create it *again* with the same name.
Now hold on here, we have tested the imp in a new database, all is fine and all we want to do is allow connections to the old database instance name?
That's pretty much a one-liner, not a new database.
We can simply add the new name we want to "listen on" to the SERVICE_NAMES parameter.
Easy peasy.

Ok, here is what we should do. Quite a long example for something simple.
But hey, just want to make it clear.

oracle@htpc:admin$ lsnrctl status
-- What's the current db_name and service_names?
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 08-JUL-2007 18:31:22

Copyright (c) 1991, 2005, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Start Date                08-JUL-2007 18:23:39
Uptime                    0 days 0 hr. 7 min. 43 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/oracle/10g/network/admin/listener.ora
Listener Log File         /u01/oracle/10g/network/log/listener.log
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=htpc)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "peggy" has 2 instance(s).
  Instance "peggy", status UNKNOWN, has 1 handler(s) for this service...
  Instance "peggy", status READY, has 1 handler(s) for this service...
Service "peggyXDB" has 1 instance(s).
  Instance "peggy", status READY, has 1 handler(s) for this service...
Service "peggy_XPT" has 1 instance(s).
  Instance "peggy", status READY, has 1 handler(s) for this service...
The command completed successfully
oracle@htpc:admin$ rsqlplus hlinden/hlinden as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jul 8 18:31:24 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL> show parameter db_name

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_name                              string      peggy
SQL> show parameter service_names

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
service_names                        string      peggy
SQL> 
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
-- What can we connect to?
oracle@htpc:admin$ rsqlplus hlinden/hlinden@//htpc/peggy

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jul 8 18:31:53 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL> 
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
oracle@htpc:admin$ rsqlplus hlinden/hlinden@//htpc/dog

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jul 8 18:31:58 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor


Enter user-name:
-- Ouch, that's the one we want!

oracle@htpc:admin$ rsqlplus hlinden/hlinden as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jul 8 18:32:01 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

-- Here is the 'one-liner'
SQL> alter system set service_names='peggy,dog' scope=spfile;

System altered.

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area  599785472 bytes
Fixed Size                  2022600 bytes
Variable Size             167772984 bytes
Database Buffers          423624704 bytes
Redo Buffers                6365184 bytes
Database mounted.
Database opened.
SQL> 
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
-- Let's see what changed. What can we connect to now?
oracle@htpc:admin$ lsnrctl status

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 08-JUL-2007 18:33:57

Copyright (c) 1991, 2005, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Start Date                08-JUL-2007 18:23:39
Uptime                    0 days 0 hr. 10 min. 18 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/oracle/10g/network/admin/listener.ora
Listener Log File         /u01/oracle/10g/network/log/listener.log
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=htpc)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "dog" has 1 instance(s).
  Instance "peggy", status READY, has 1 handler(s) for this service...
Service "peggy" has 2 instance(s).
  Instance "peggy", status UNKNOWN, has 1 handler(s) for this service...
  Instance "peggy", status READY, has 1 handler(s) for this service...
Service "peggyXDB" has 1 instance(s).
  Instance "peggy", status READY, has 1 handler(s) for this service...
Service "peggy_XPT" has 1 instance(s).
  Instance "peggy", status READY, has 1 handler(s) for this service...
The command completed successfully
oracle@htpc:admin$ rsqlplus hlinden/hlinden@//htpc/dog

SQL*Plus: Release 10.2.0.1.0 - Production on Sun Jul 8 18:34:18 2007

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
-- It works, but where are we?

SQL> select sys_context('userenv','SERVICE_NAME') from dual;

SYS_CONTEXT('USERENV','SERVICE_NAME')
------------------------------------------------------------------------------------------------------------------------
dog

SQL> select sys_context('userenv','DB_NAME') from dual;

SYS_CONTEXT('USERENV','DB_NAME')
------------------------------------------------------------------------------------------------------------------------
peggy

The new top 500 supercomputer list is out!

Finally had some time to look at the latest Top500 supercomputer list released last week at ISC '07 last week.

Lots of changes compared to the old list; two quite interesting new things. First of all is Intel multi-core chips, secondly we have Blades, loads and loads of blades.
A significant number of entries on the list are using Intel Xeon 5160 3.0GHz dual-core CPU's and there is also a number of quad-core systems.
Another interesting point is that the crown in terms of number of systems on the list has been passed from IBM (with 192 systems) to HP (with 201 systems).
The HP Cluster Platform BL460c holds quite a few spots on the list. Can't say I've heard much about HP's HPC offering so far, they're not exactly beating the drum on that one (compared to the IBM guy who's calling me every 2 months).

SGI holds a few new slots on the list as well, which is extra fun to see considering the hard last year SGI have had. One Altix system even made it to number 10 on the list (with Columbia on number 13).