Coding practices

Here is a good short article from a guy called Jackson about coding practices. Take a few moments to read the article and ask yourself if you may should change something on your coding style!

NYOUG Meeting – 25th anniversary

It’s a long time since I have posted something here, I know. As you might remember from my last post I moved over to New York and well, there where a lot of things to do the last months. Anyway, I’m not writing here to make excuses. Fact is that I have been very busy lately. In my (new) role as “Performance Engineer” in the company I got new tasks beside my Oracle tuning stuff. Actually I spent most of the time in the last few months with tuning our Java application and not Oracle anymore. But I’m happy with that as this gave and still gives me the opportunity to learn more about the art of tuning! But this just as a short clarification why my Oracle related posts are so rare lately.

Anyway, today I had the chance to attend the New York Oracle User Group meeting together with my working colleagues. This was my first user group meeting at all so I was a little bit excited about what will be waiting for me there! As I took this serious I printed off the agenda already a few days back and marked the sessions which seemed to be interesting for me. One great thing I discovered was a session with Tanel Poder who I already know because of his blog (which I have also in my Blogroll of course!). Tanel is one of the few guys who shares his scripts with you. Most of the DBAs hide their secret, magic scripts for themselves to be the number 1 DBA. But Tanel provides his scripts to the world. You can download the whole catalog as a simple zip file from his website and well believe me he has a lot of scripts! Anyway, from the four sessions I have chosen three of them where performance related. Actually all of the sessions that I wanted to attend were performance related but unfortunately the first session about performance on SSD was canceled so I attended Arup Nandas session about upgrading to 11g and how database replay/standby database can help you minimize the downtime. Actually I had such a session already back in February in Vienna at Oracle so there weren’t really new things for me at the presentation. The second session was then the one from Tanel. It was about (his) scripts and tools that (can) make your life easier. Third session was from Dave Anderson about 11g Result-Set Cache. He did some life demos on it what was really cool. It gave you the chance to see result set cache really working and improving your performance at the response time. Fourth and last session was from Dean Richards  – “Advanced SQL tuning”. This was a very, very interesting session as he had some real world issues in the presentation. He also gave an overview on which steps are important for performance tuning (knowing the background, triggering down the issue, etc.) After the sessions there were some vendor raffles. I hoped to win the 32″ TV but of course I did not! Actually I didn’t win anything! ;(

If I have to rate the sessions I attended then I would say that the best presenter was Tanel Poder. He was agile and brought some nice “real world” jokes into the session. There was not a single second in his session where you got bored or did pay more attention to your Blackberry than to him! The best session rated by the content would have been Dean Richards “Advanced SQL tuning”. He showed up important things about how to tune and how important it is to understand the whole story around it!

Well time for pictures:

Times have changed

It has been already some time that I posted something here and I’m sorry for that but there are good reasons for it. First and most important thing is that I’ll go to New York at 5th of October – business related – and stay there 1 and a half year according to the current plan. The second thing is that my company unfortunately decided to close our office here in Austria due to money saving plans – financial crisis. So you can guess that we had a lot of other things to do then. For my german readers I started a new web site where you can follow me on my trip in New York: www.venzi.net Of course I’ll continue this blog but this one will become a pure tech blog related to my experiences in the IT industry. And that brings me already to two points:

• I’ve updated my MacBook successfully to snow leopard!
• Oracle 11g Release 2 is out!

That’s one small step for a man, one giant leap for mankind

Today is the 40th anniversary of the Apollo 11 moon landing. It’s just 40 years ago that Neil Armstrong made his first steps on the moon. After him just 11 other people had the same honor. The Apollo missions ended in December 1972 and with them the men walking on the satellite.

USB tools you must have

I’m sure you know the important USB tools like a USB coffee cup warmer or a USB ventilator without the IT wouldn’t work anymore. Now there is another (useless) tool, the i.Saw.

Yeah, now I’m able to cut trees with my MacBook and that for just 60 dollars!

How sweet 4 GB can be

Finally I upgraded my MacBook to 4GB RAM. I wanted that long before but I never did it. Actually I don’t know why. I guess there were some factors which hold me up. But now I got 2 2GB RAM bars for 53 Euros which isn’t really much and I decided to do it – well some OutOfMemory help me with the decision

But now I’m just happy having 4GB in my MacBook and that thing is really fast again *yepee*

Oracle 10g enqueue waits

Just found a useful list of Oracle 10g enqueue waits in the web which I don’t want to deprive from you:

Enqueue Type	Description
enq: AD – allocate AU	Synchronizes accesses to a specific OSM (Oracle Software Manager) disk AU
enq: AD – deallocate AU	Synchronizes accesses to a specific OSM disk AU
enq: AF – task serialization	Serializes access to an advisor task
enq: AG – contention	Synchronizes generation use of a particular workspace
enq: AO – contention	Synchronizes access to objects and scalar variables
enq: AS – contention	Synchronizes new service activation
enq: AT – contention	Serializes alter tablespace operations
enq: AW – AW$ table lock	Allows global access synchronization to the AW$ table (analytical workplace tables used in OLAP option)
enq: AW – AW generation lock	Gives in-use generation state for a particular workspace
enq: AW – user access for AW	Synchronizes user accesses to a particular workspace
enq: AW – AW state lock	Row lock synchronization for the AW$ table
enq: BR – file shrink	Lock held to prevent file from decreasing in physical size during RMAN backup
enq: BR – proxy-copy	Lock held to allow cleanup from backup mode during an RMAN proxy-copy backup
enq: CF – contention	Synchronizes accesses to the controlfile
enq: CI – contention	Coordinates cross-instance function invocations
enq: CL – drop label	Synchronizes accesses to label cache when dropping a label
enq: CL – compare labels	Synchronizes accesses to label cache for label comparison
enq: CM – gate	Serializes access to instance enqueue
enq: CM – instance	Indicates OSM disk group is mounted
enq: CT – global space management	Lock held during change tracking space management operations that affect the entire change tracking file
enq: CT – state	Lock held while enabling or disabling change tracking to ensure that it is enabled or disabled by only one user at a time
enq: CT – state change gate 2	Lock held while enabling or disabling change tracking in RAC
enq: CT – reading	Lock held to ensure that change tracking data remains in existence until a reader is done with it
enq: CT – CTWR process start/stop	Lock held to ensure that only one CTWR (Change Tracking Writer, which tracks block changes and is initiated by the alter database enable block change tracking command) process is started in a single instance
enq: CT – state change gate 1	Lock held while enabling or disabling change tracking in RAC
enq: CT – change stream ownership	Lock held by one instance while change tracking is enabled to guarantee access to thread-specific resources
enq: CT – local space management	Lock held during change tracking space management operations that affect just the data for one thread
enq: CU – contention	Recovers cursors in case of death while compiling
enq: DB – contention	Synchronizes modification of database wide supplemental logging attributes
enq: DD – contention	Synchronizes local accesses to ASM (Automatic Storage Management) disk groups
enq: DF – contention	Enqueue held by foreground or DBWR when a datafile is brought online in RAC
enq: DG – contention	Synchronizes accesses to ASM disk groups
enq: DL – contention	Lock to prevent index DDL during direct load
enq: DM – contention	Enqueue held by foreground or DBWR to synchronize database mount/open with other operations
enq: DN – contention	Serializes group number generations
enq: DP – contention	Synchronizes access to LDAP parameters
enq: DR – contention	Serializes the active distributed recovery operation
enq: DS – contention	Prevents a database suspend during LMON reconfiguration
enq: DT – contention	Serializes changing the default temporary table space and user creation
enq: DV – contention	Synchronizes access to lower-version Diana (PL/SQL intermediate representation)
enq: DX – contention	Serializes tightly coupled distributed transaction branches
enq: FA – access file	Synchronizes accesses to open ASM files
enq: FB – contention	Ensures that only one process can format data blocks in auto segment space managed tablespaces
enq: FC – open an ACD thread	LGWR opens an ACD thread
enq: FC – recover an ACD thread	SMON recovers an ACD thread
enq: FD – Marker generation	Synchronization
enq: FD – Flashback coordinator	Synchronization
enq: FD – Tablespace flashback on/off	Synchronization
enq: FD – Flashback on/off	Synchronization
enq: FG – serialize ACD relocate	Only 1 process in the cluster may do ACD relocation in a disk group
enq: FG – LGWR redo generation enq race	Resolves race condition to acquire Disk Group Redo Generation Enqueue
enq: FG – FG redo generation enq race	Resolves race condition to acquire Disk Group Redo Generation Enqueue
enq: FL – Flashback database log	Synchronizes access to Flashback database log
enq: FL – Flashback db command	Synchronizes Flashback Database and deletion of flashback logs
enq: FM – contention	Synchronizes access to global file mapping state
enq: FR – contention	Begins recovery of disk group
enq: FS – contention	Synchronizes recovery and file operations or synchronizes dictionary check
enq: FT – allow LGWR writes	Allows LGWR to generate redo in this thread
enq: FT – disable LGWR writes	Prevents LGWR from generating redo in this thread
enq: FU – contention	Serializes the capture of the DB feature, usage, and high watermark statistics
enq: HD – contention	Serializes accesses to ASM SGA data structures
enq: HP – contention	Synchronizes accesses to queue pages
enq: HQ – contention	Synchronizes the creation of new queue IDs
enq: HV – contention	Lock used to broker the high watermark during parallel inserts
enq: HW – contention	Lock used to broker the high watermark during parallel inserts
enq: IA – contention	Information not available
enq: ID – contention	Lock held to prevent other processes from performing controlfile transaction while NID is running
enq: IL – contention	Synchronizes accesses to internal label data structures
enq: IM – contention for blr	Serializes block recovery for IMU txn
enq: IR – contention	Synchronizes instance recovery
enq: IR – contention2	Synchronizes parallel instance recovery and shutdown immediate
enq: IS – contention	Synchronizes instance state changes
enq: IT – contention	Synchronizes accesses to a temp object’s metadata
enq: JD – contention	Synchronizes dates between job queue coordinator and slave processes
enq: JI – contention	Lock held during materialized view operations (such as refresh, alter) to prevent concurrent operations on the same materialized view
enq: JQ – contention	Lock to prevent multiple instances from running a single job
enq: JS – contention	Synchronizes accesses to the job cache
enq: JS – coord post lock	Lock for coordinator posting
enq: JS – global wdw lock	Lock acquired when doing wdw ddl
enq: JS – job chain evaluate lock	Lock when job chain evaluated for steps to create
enq: JS – q mem clnup lck	Lock obtained when cleaning up q memory
enq: JS – slave enq get lock2	Gets run info locks before slv objget
enq: JS – slave enq get lock1	Slave locks exec pre to sess strt
enq: JS – running job cnt lock3	Lock to set running job count epost
enq: JS – running job cnt lock2	Lock to set running job count epre
enq: JS – running job cnt lock	Lock to get running job count
enq: JS – coord rcv lock	Lock when coord receives msg
enq: JS – queue lock	Lock on internal scheduler queue
enq: JS – job run lock – synchronize	Lock to prevent job from running elsewhere
enq: JS – job recov lock	Lock to recover jobs running on crashed RAC inst
enq: KK – context	Lock held by open redo thread, used by other instances to force a log switch
enq: KM – contention	Synchronizes various Resource Manager operations
enq: KP – contention	Synchronizes kupp process startup
enq: KT – contention	Synchronizes accesses to the current Resource Manager plan
enq: MD – contention	Lock held during materialized view log DDL statements
enq: MH – contention	Lock used for recovery when setting Mail Host for AQ e-mail notifications
enq: ML – contention	Lock used for recovery when setting Mail Port for AQ e-mail notifications
enq: MN – contention	Synchronizes updates to the LogMiner dictionary and prevents multiple instances from preparing the same LogMiner session
enq: MR – contention	Lock used to coordinate media recovery with other uses of datafiles
enq: MS – contention	Lock held during materialized view refresh to set up MV log
enq: MW – contention	Serializes the calibration of the manageability schedules with the Maintenance Window
enq: OC – contention	Synchronizes write accesses to the outline cache
enq: OL – contention	Synchronizes accesses to a particular outline name
enq: OQ – xsoqhiAlloc	Synchronizes access to olapi history allocation
enq: OQ – xsoqhiClose	Synchronizes access to olapi history closing
enq: OQ – xsoqhistrecb	Synchronizes access to olapi history globals
enq: OQ – xsoqhiFlush	Synchronizes access to olapi history flushing
enq: OQ – xsoq*histrecb	Synchronizes access to olapi history parameter CB
enq: PD – contention	Prevents others from updating the same property
enq: PE – contention	Synchronizes system parameter updates
enq: PF – contention	Synchronizes accesses to the password file
enq: PG – contention	Synchronizes global system parameter updates
enq: PH – contention	Lock used for recovery when setting proxy for AQ HTTP notifications
enq: PI – contention	Communicates remote Parallel Execution Server Process creation status
enq: PL – contention	Coordinates plug-in operation of transportable tablespaces
enq: PR – contention	Synchronizes process startup
enq: PS – contention	Parallel Execution Server Process reservation and synchronization
enq: PT – contention	Synchronizes access to ASM PST metadata
enq: PV – syncstart	Synchronizes slave start_shutdown
enq: PV – syncshut	Synchronizes instance shutdown_slvstart
enq: PW – prewarm status in dbw0	DBWR0 holds this enqueue indicating pre-warmed buffers present in cache
enq: PW – flush prewarm buffers	Direct Load needs to flush prewarmed buffers if DBWR0 holds this enqueue
enq: RB – contention	Serializes OSM rollback recovery operations
enq: RF – synch: per-SGA Broker metadata	Ensures r/w atomicity of DG configuration metadata per unique SGA
enq: RF – synchronization: critical ai	Synchronizes critical apply instance among primary instances
enq: RF – new AI	Synchronizes selection of the new apply instance
enq: RF – synchronization: chief	Anoints 1 instance’s DMON (Data Guard Broker Monitor) as chief to other instance’s DMONs
enq: RF – synchronization: HC master	Anoints 1 instance’s DMON as health check master
enq: RF – synchronization: aifo master	Synchronizes critical apply instance failure detection and failover operation
enq: RF – atomicity	Ensures atomicity of log transport setup
enq: RN – contention	Coordinates nab computations of online logs during recovery
enq: RO – contention	Coordinates flushing of multiple objects
enq: RO – fast object reuse	Coordinates fast object reuse
enq: RP – contention	Enqueue held when resilvering is needed or when data block is repaired from mirror
enq: RS – file delete	Lock held to prevent file from accessing during space reclamation
enq: RS – persist alert level	Lock held to make alert level persistent
enq: RS – write alert level	Lock held to write alert level
enq: RS – read alert level	Lock held to read alert level
enq: RS – prevent aging list update	Lock held to prevent aging list update
enq: RS – record reuse	Lock held to prevent file from accessing while reusing circular record
enq: RS – prevent file delete	Lock held to prevent deleting file to reclaim space
enq: RT – contention	Thread locks held by LGWR, DBW0, and RVWR (Recovery Writer, used in Flashback Database operations) to indicate mounted or open status
enq: SB – contention	Synchronizes logical standby metadata operations
enq: SF – contention	Lock held for recovery when setting sender for AQ e-mail notifications
enq: SH – contention	Enqueue always acquired in no-wait mode – should seldom see this contention
enq: SI – contention	Prevents multiple streams table instantiations
enq: SK – contention	Serialize shrink of a segment
enq: SQ – contention	Lock to ensure that only one process can replenish the sequence cache
enq: SR – contention	Coordinates replication / streams operations
enq: SS – contention	Ensures that sort segments created during parallel DML operations aren’t prematurely cleaned up
enq: ST – contention	Synchronizes space management activities in dictionary-managed tablespaces
enq: SU – contention	Serializes access to SaveUndo Segment
enq: SW – contention	Coordinates the ‘alter system suspend’ operation
enq: TA – contention	Serializes operations on undo segments and undo tablespaces
enq: TB – SQL Tuning Base Cache Update	Synchronizes writes to the SQL Tuning Base Existence Cache
enq: TB – SQL Tuning Base Cache Load	Synchronizes writes to the SQL Tuning Base Existence Cache
enq: TC – contention	Lock held to guarantee uniqueness of a tablespace checkpoint
enq: TC – contention2	Lock during setup of a unique tablespace checkpoint in null mode
enq: TD – KTF dump entries	KTF dumping time/scn mappings in SMON_SCN_TIME table
enq: TE – KTF broadcast	KTF broadcasting
enq: TF – contention	Serializes dropping of a temporary file
enq: TL – contention	Serializes threshold log table read and update
enq: TM – contention	Synchronizes accesses to an object
enq: TO – contention	Synchronizes DDL and DML operations on a temp object
enq: TQ – TM contention	TM access to the queue table
enq: TQ – DDL contention	DDL access to the queue table
enq: TQ – INI contention	TM access to the queue table
enq: TS – contention	Serializes accesses to temp segments
enq: TT – contention	Serializes DDL operations on tablespaces
enq: TW – contention	Lock held by one instance to wait for transactions on all instances to finish
enq: TX – contention	Lock held by a transaction to allow other transactions to wait for it
enq: TX – row lock contention	Lock held on a particular row by a transaction to prevent other transactions from modifying it
enq: TX – allocate ITL entry	Allocating an ITL entry in order to begin a transaction
enq: TX – index contention	Lock held on an index during a split to prevent other operations on it
enq: UL – contention	Lock held used by user applications
enq: US – contention	Lock held to perform DDL on the undo segment
enq: WA – contention	Lock used for recovery when setting watermark for memory usage in AQ notifications
enq: WF – contention	Enqueue used to serialize the flushing of snapshots
enq: WL – contention	Coordinates access to redo log files and archive logs
enq: WP – contention	Enqueue to handle concurrency between purging and baselines
enq: XH – contention	Lock used for recovery when setting No Proxy Domains for AQ HTTP notifications
enq: XR – quiesce database	Lock held during database quiesce
enq: XR – database force logging	Lock held during database force logging mode
enq: XY – contention	Lock used by Oracle Corporation for internal testing

Of course I don’t want to steal anyones content here:

Found at: http://oracle-dox.net/

Direct link: http://oracle-dox.net/McGraw.Hill-Oracle.Wait.Interf/8174final/LiB0063.html

Many thanks to Oracle-Dox for providing this table!

Vacation is over

Hi again!

Unfortunately my vacation is over and I’m back from Cuba. Well the vacation was great of course! The Cuban are great and especially releaxed people and the landscape is really as like in the movie “Pirates of the Caribbean”! Of course I brought over some cigars and rum. And I smoked some of them right in Cuba because only there you’ve the right feeling for it! I also had a little salsa session but I’m not the born dancer!

Anyway, pictures aren’t online yet – seems that some people were waiting for me! But I look forward to have them online in the next 1 – 2 weeks!

So all in all it’s time to update my list of visited countries:

visited 13 states (5.77%)
Create your own visited map of The World

Vacation: Cuba

Well, I promised some more posts the last time but the problem is that I’m very busy in the last couple of weeks – in work as also in my freetime. One of the reasons is definitely that I’m going on vacation on Thursday and it looks like that everyone is thinking that I won’t return anymore! But back to the positiv things: The destination this time is Cuba.

I have spoken already three or four years ago that I want to visit this country once. One of the main reasons was that when you’re in Cuba you make a time travel back to the 60s. Last year a working colleague was with his girlfriend there and as I saw the photos I was sure that this year it will be Cuba. I had a little bit of luck: We started talking about Cuba in February and my colleague told us that we’re already very late. You can’t/won’t visit Cuba in the summer because of the hurricane season which starts in the middle of May and ends somewhere in October. So we hurried up and made a visit in the travel agency and we fortunately got one of the last seats on a tour between 9th of April till 24th of April.

The vacation is split up in two main parts:

The first 8 days we make a round trip through whole Cuba, the other 7 days we’re in an all-inclusive hotel in Varadero and just relax.

Hopefully everything will go fine but I’m confident!

So, we’ll read us in 2 and a half weeks – and no, the cigars are for me and only for me!

Cheers,

When developers go for a coffee

Seems that the developer forgot something when we coded an exception throw.

I guess we went for a coffe before he checked the code in!