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VMWare Hires Redis Key Developer – But Why?

My friend MosheZ alerted me to the fact (which few hours later appeared all over the net) that VMWare hired Redis key developer. Which is as close to acquisition as you can get with an open source project.

What is Redis? Redis is yet-another-NoSQL. A key-value store, somewhat similar to Tokyo Cabinet. Except that Redis does persistence differently, which makes it faster in many cases. Redis started as a Memcached replacement, so a lot of the documentation describes it as follows: Redis is like Memcached, except it supports more data types, it is persistent to some degree and it is not distributed.

But the more interesting question is – Why does VMWare need Redis?

VMWare says: “As VMware continues its investments in the context of cloud computing, technologies such as Redis become key for future cloud based apps, whether private or public cloud, and the cloud infrastructure itself.”

So Redis is cloud and VMWare is a major cloud player, therefore VMWare needs redis. Two discrepancies stand out in this story:

  1. Redis is not distributed system. Unlike Cassandra, where you can scale by quickly adding more Cassandras to the party, Redis is just one (very fast) server, only supporting master-slave replication. VMWare is all about adding new machines quickly. Something doesn’t fit.
  2. While key-value stores are  cloudy and VMWare is cloudy, there is no natural match between their cloudiness. VMWare itself can’t use Redis – because Redis technology is a natural match for big-data websites which VMWare clearly isn’t. Some VMWare customers can benefit from Redis, but most can’t. What’s going on here?

Clearly, the place to look is not in existing value but in the future. So here are my predictions:

  1. Redis will become distributed. It can certainly be done. Perhaps it can even be done without losing it’s performance edge.
  2. VMware will announce an Amazon-like, cloud-for-rent service. They have the technology for this, and Redis will help them manage the “huge website” part of it.
  3. They may also offer Redis on top of the virtual servers, as something built in. Like Amazon’s Oracle servers.
  4. VMWare can also offer storage for rent. They can do it with EMC storage (since VMWare is an EMC company), but I’m betting that they’ll do it with Netapp – their favorite cloud partner.  I can totally imagine a near-future Netapp-Vmware offering that is similar to Amazon’s EC2+ S3+AWS.

Predicting is very difficult (especially about the future) and I’m very much ready to regret ever posting my day dreams in public, but these are exciting possibilities. I wonder if they make sense to anyone else.

*********************************

And speaking of MosheZ, he is a prolific song writer, and he wrote a song about DBAs! I’m thinking of performing it live during one of my presentations. Actually I’m thinking of writing a presentation “How to win arguments or influence users” just to have an excuse to sneak this song in :)

managing statistics on partitions

The best methods for managing statistics in general on Oracle is an area that has yet to well ironed out but when it comes to partitions is all the more challenging. Doug Burns is putting together a set of blog post attempting to iron out some of the issue :

  • Part 1 – In which we see a simple example and do a default stats collection
  • Part 2 – In which we consider Global Stats
  • Part 3 – In which subpartitions and aggregation cause problems
  • Part 4 – In which our hero fights his way through stats aggregation woes
  • Part 5 - In which we encounter a partition exchange
Nice aggregated listing via Jonathan Lewis

Trending with Statspack

Anjo use to do statspack analysis at oraperf.com which has been out of order every time I've looked over the past few years.

Tim Gorman published scripts years ago to output trending reports on statspack which AFAIK are still a valid resource today.
But now I see there is a web site to upload zips of statspack reports and output graphical trending reports. Looks interesting:

Monitoring SQL run on MySQL

Nice example of using Wireshark to monitor what's getting run on MySQL.

I played around with something similar for Oracle didn't get to far. It's an interesting idea for monitoring,auditing and/or creating replay scripts.

Bug or Feature

I love this little cartoon

which is a funny story about why OEM DB Control wouldn't start up because the hostname started with a "U" believe it or not (read the blog post for more info!). It's yet another reason why I have issues with OEM. When OEM fails to work it can be exasperating. Just last week I was watching a presentation one OEM where OEM wouldn't start for 20 minutes - provide for quick thinking on the presenters part to fill in that 20 minute hole. I was tempted to run up to the presenter and give them a DVD with instant on DB Optimizer which require no agents and no install. Just put the DVD in (also available via free download) and click on the executable and point it at any database (SQL Server, Sybase, DB2 or Oracle ) and voila you get a load chart of average active sessions and a breakdown on where the load is coming from immediately.

What Bind Variable values were used in my Query

Check out this query by Kerry Osborne via Oracle-L (archives at Oracle-l Archives) for getting the peeked bind variable values from v$sql_plan. These values are in a raw format so the following query requires a function to decode the values. See the function code listing at the end
col bind_name for a20
col bind_type for a20
col value for a40
select
bind_name,
decode(bind_type,1,'VARCHAR2',2,'NUMBER',bind_type) bind_type,
decode(bind_type,1,display_raw(bind_data,'VARCHAR2'),2,display_raw(bind_data,'NUMBER'),bind_data) value
from (
select
extractvalue(value(d), '/bind/@nam') as bind_name,
extractvalue(value(d), '/bind/@dty') as bind_type,
extractvalue(value(d), '/bind') as bind_data
from
xmltable('/*/*/bind'
passing (
select
xmltype(other_xml) as xmlval
from
v$sql_plan
where
sql_id like nvl('&sql_id',sql_id)
and child_number = '&child_no'
and other_xml is not null
)
) d
)
;
create or replace function display_raw (rawval raw, type varchar2)
return varchar2
is
cn number;
cv varchar2(32);
cd date;
cnv nvarchar2(32);
cr rowid;
cc char(32);
begin
if (type = 'NUMBER') then
dbms_stats.convert_raw_value(rawval, cn);
return to_char(cn);
elsif (type = 'VARCHAR2') then
dbms_stats.convert_raw_value(rawval, cv);
return to_char(cv);
elsif (type = 'DATE') then
dbms_stats.convert_raw_value(rawval, cd);
return to_char(cd,'dd-mon-yyyy');
elsif (type = 'NVARCHAR2') then
dbms_stats.convert_raw_value(rawval, cnv);
return to_char(cnv);
elsif (type = 'ROWID') then
dbms_stats.convert_raw_value(rawval, cr);
return to_char(cnv);
elsif (type = 'CHAR') then
dbms_stats.convert_raw_value(rawval, cc);
return to_char(cc);
else
return 'UNKNOWN DATATYPE';
end if;
end;
/
Interesting to note that the v$sql_bind_capture has captured bind variables but not necessarily the ones that were peeked at optimization and these captured values can be recaptured without being used in the optimization of the query. From http://jonathanlewis.wordpress.com/2008/07/24/bind-capture/

by using an ‘alter system’ call to change the “_cursor_bind_capture_interval” to a (performance-threatening) 10 seconds on a small test system, I found that the values in v$sql_bind_capture would change fairly regularly as I re-executed a given query with constantly changing input bind values.

further reading about bind vars from the errorstack by Tanel:

My New Laptop

One more post that's only vaguely related to Oracle and then back to the stats posts.

I mentioned previously that I'd ordered myself one of these. After suffering performance problems with my 11.2/OEL/VMWare/Parallelism demos at UKOUG, I was determined that wouldn't happen again and that it was time for a new laptop, complete with Core i7, 8G RAM and an SSD. In the event, Dell came up with a 6 week lead-time, so I cancelled the order. Of course, as soon as I did that, they solved their lead-time issues and raised a new order on my behalf which I'm still trying to get returned! But that's another story.

I started to look at alternatives (but there weren't many because the laptop Core i7 hasn't been available long) and came across the Sony VPCF11Z1E. No SSD, but a Blu-Ray drive and I've been more than happy with my previous Vaio over the last couple of years. Better still, my mate Jari checked out John Lewis and I could pick one up the next day. It all looked a bit consumer/multimedia orientated and I was a bit concerned about the dimensions and weight, but performance was the main priority and I could always stick an SSD in it later if I decided that would help. The other issue (and I was talking to another conference speaker who had shared this experience) was that I'd left it late, the conference was approaching and so it was a bit of a hurried purchase. If Apple had a Core i7 model out now, that would have been on the list too.

The next day it turned up with the minimum of fuss (John Lewis are great) and I opened the box excitedly. Only to feel let down :-(

The thing just seemed so big and heavy. Worse, still, when I powered it on and started using it, I noticed the fan noise as much as the absolutely stunning screen. Definitely not in the same league as the ISP4400 in the bedroom, but the laptop equivalent. Mmmm. Not the "isn't my new toy great" moment I'd been expecting. It also didn't fit into my existing laptop bag which was a key part of my smooth operation commuting to London. In fact, it was difficult to see why I'd bothered and I kept looking longingly at my old Vaio as I moved stuff between the two machines.

Mads insisted she thought it was great, as did Jari (but then he would, having talked me into it! LOL), but I was searching for things to like about it. Eventually they started to appear and I've become much happier with it over the past few weeks.

- The screen is simply stunning and one benefit of a wide screen is that it's not a bad replacement for the dual monitor set-up at work. Tom Kyte is right - screen estate is a big deal.

- Throw in Blu-Ray and should I ever want to watch a movie it's amazing, based on my first experience with District 9.

- I love Sony keyboards.

- I hate numeric keypads and offset keyboards on a laptop. Might be useful if I played games a bit more.

- I ran the same Swingbench tests on the old and new laptop against the same VM (and no, I'm not going into details - this is consistent across many different tests). Old laptop - 35,000 Transactions Per Minute. New laptop - 180,000 TPM. Ah! Now I remember why I bought it* ;-)

- Despite it being a bit bigger than I'd like, it's nowhere near as bad as Marco managed to make it look in this carefully-arranged stunt-shot!

By the time I reached Hotsos, I was feeling much better about it and when Kevin Closson was talking about the advantages and disadvantages of SMT, I was keen to try it. Damn! Consumer-grade nonsense again! I've never seen fewer BIOS options in my life! Date/Time, system password and a solitary option to enable VT. So at least Sony let you enable VT now which is an improvement on the past, but ... sigh. I'm going to have to go hunting for ways of accessing more advanced BIOS options so that I can break my next set of demos ;-)

All in all, I'm happy I bought it now, but it's definitely not recommended if you're a road warrior. Even with my new rucksack, it's a little on the heavy side and you can imagine how quickly you can tear through battery power (particularly if you decide to run intensive benchmarks)!

*Top tip, though. It doesn't matter how powerful your new laptop is and how elegantly VMWare allows you to move your demos on to it, if you forget to install the Windows Loopback Adaptor, it will all count for nothing and you'll look and feel like a clown ;-)

P.S. Couldn't resist sneaking a look in that Dell box, wondering if I'd made a mistake. What a relief. It was just as big, seemed heavier, looked pretty but I'd definitely rather have the Sony!

Hotsos 2010 - Summary

[One thing that's great about jet-lag is that it allows you to catch up on blogging and all the email that's built up while you've been away at the conference. Not much else you can do at 2:30 in the morning.]

I'm glad I went to the Hotsos Symposium again this year. Attending conferences is an expensive business when you're a contractor as it means more lost income, so I can't go to every conference I'd like to attend but this one should probably remain near the top of my list.

Lows

- My presentation, obviously. There was a funny moment in the office today when I was looking at the OEM Top Activity page - because, yet again, it had highlighted a performance problem we were previously unaware of - and our architect said perhaps I shouldn't be using it because I couldn't be trusted not to break OEM! ;-)

- Somehow contriving to miss both of Richard Foote's presentations but at least I was able to enjoy his entertaining company at dinner one night.

- The weather - not what I had in mind at all!

Highs

- The people, as always. Not only are there lots of smart speakers and attendees at Hotsos, but the informal setting makes it easier to catch up with them. It was particularly good to get time to speak properly to a few people I've only met briefly before, buy Kerry Osborne that beer and to see Polish Paul Matuszyk there after I recommended it to him 4 years ago! As for Monique, she's one of a kind ;-)

- Disco Night. Can I request that we have more party nights themed on women wearing glittery mini-dresses and Oracle geeks dancing in duck costumes?

- Alex G playing chopsticks on the piano in a large suite. I was expecting something a little more elegant!

- Quite a few presentations, not least, Bob Sneed's CPU QoS, Kevin Closson ranting intelligently about where we are today and where we're heading, Alex G reducing the room to fits of laughter whilst reinforcing the Battle Against Any Guess message and Wolfgang's Anatomy of a SQL Tuning Session.

- Feeling inspired to think about performance even more now that I'm back in the office.

So, expensive or not, I'm glad I went but next year I might stick to text-mode demos that don't need a network connection!

Hotsos 2010 - Day 5 - Training Day with Tanel Poder

I generally wouldn't visit the Hotsos Training Day, mainly because I've been away from home and work for long enough, particularly when you add the travelling time at either end, but this time I was determined to attend because Tanel was presenting.

It was a busy room with a very high percentage of attendees staying for the additional day. I suppose once people were actually allowed out of the office in the current economic climate, they figured they might as well pack in as much learning as they could. Tanel described it as one of the peaks of his career and I can understand that. It's an honour to present at the Symposium, so a whole day must be a pretty special privliege, but he's more than earned it with the number of good presentations and blog posts he's come up with.

It didn't get off to a good start, though, as there was a problem with the focus of the projectors, but that was soon adjusted a little and people were happy as long as it was good enough to read the text.

Speaking of text, he kicked off spending quite a bit of time talking about using the right tools for the job - sqlplus, basically ;-) - and how we can make our own performance more efficient before we even start looking at performance issues. Make no mistake - despite having a love of pictures these days, I'm fundamentally a command line chap who frequently finds himself doing the things Tanel talked about, which consequently made me chuckle.

- When diagnosing Oracle problems reported by others, I ask them to stop using TOAD, their JDBC application or whatever it is they're using and login to sqlplus. Once the problem is recreated there, I know it's a real problem.

- On windows I use the CMD prompt version of sqlplus too and can't stand sqlplusw (but I should perhaps keep that quiet because lots of others seem to like it ;-) )

- On Linux he spent a lot of time on RLWRAP and command line completion and there were some really good ideas in there that I don't use enough so I'm going to revisit them.

He showed some neat and entertaining tricks with colours that I took some photos of but they wouldn't really do them justice. I'm expecting him to have a movie playing from sqlplus next year ;-)

While talking about his Snapper tool, he drew the comparisons between it and ASH data, which he was pretty positive about and mentioned how ASH data is like a DW fact table with multiple dimensions that allow flexible and relatively complex drill-down into specific dimensions to help diagnose performance issues. That's something I talk about quite a lot when I'm teaching people about ASH.

But he came at it more from the angle of his own Snapper tool, which is cool if you've never taken a look and between that and the section on latchprof and latchprofx, demonstrated pretty effectively that these tools allow you to look at most problems and to limit your investigations to those that matter. For example, for someone who is known for his work on diagnosing latch contention problems (amongst other things) he was very careful to point out that you shouldn't become obsessed by latch contention unless it's causing a problem! He didn't stop there, though, next up was the utility that I know a few people have been waiting for - the Mother Of All Tuning Scripts, or MOATS.

I wouldn't want to steal any of Tanel's thiunder by blogging about it in too much detail, I'm sure he'll do that himself, but MOAT is a bit like a top utility for Oracle. Although other such tools exist, e.g. OraTop, I've had a quick look and I think MOAT is probably more extensive and only requires some PL/SQL and SQL. I was pleased to see him acknowledge that it was something that he worked on with Adrian Billington who is the guy behind oracle-developer.net and someone who I've enjoyed a few beers with since I started working in London again.

Next up were SQL Performance Tools and thank goodness he re-emphasised that using the EXPLAIN PLAN FOR command is asking for trouble, particularly as there are far better tools these days to look at the plan from the child cursor instead. (My TOAD equivalent for this in the office is to berate people for using that bl**dy ambulance! LOL)

Unfortunately there were some growing Production problems at work that demanded my attention
so I had to bail out early to work in my room which meant that I missed
most of the SQL Tuning and Visualisation sections but I knew the Perfsheet content
already and you can count on me revisiting the whole day once I'm back
in the office. I particularly liked his course notes - not too detailed
to be unwieldy, but just enough detail to remind me of the day.

Although it was a really enjoyable day, I obviously knew a lot of the content already, partly because I have similar interests and partly from reading Tanel's blog. It made me wonder why people who go to Hotsos don't read blogs and stuff
the rest of the year, because I sensed a lot of the content was completely new to some others in the room. I suppose now they've found his blog, they might start.

After a few hours working in my room, things were sorted out and I could go to the bar across the street for a burger and a few beers with Marco. As soon as we walked in, Tanel shouted over and there were was an interesting little crew in there, with Tanel basking in the glow of a job well done. It was a shame about the incredibly loud karaoke or I might have stayed longer but it's safer to keep me away from karaoke - although I was quite looking forward to the Estonian version ;-) It was a good evening, though, and ended up with quite a few of us in the hotel bar. My main memories are of me defending 'my' pictures and Tanel and I praising Mr. Billington to the heavens.

The "Adrian Billington must be allowed out to a conference" campaign starts here! We won't take no for an answer.

Hinting Dynamically Generated SQL in Application Engine

One of the clever things you can do in Application Engine is dynamically generate parts of a SQL statement.  However, this can produce challenges should decide that you also need to add an optimiser hint to a SQL statement.  In this post I want to demonstrate how you can also use the same techniques to dynamically generate valid Optimizer hints.

The following statement was generated by a step in a delivered Application Engine that had not been previously been changed.  The PS_XXX tables are custom tables, but the references are in custom meta-data that is used to dynamically generate the SQL.  I have added the hints and comments. 

The specific hints and comments are not important here, the point is how I managed to generate them.

Note that:

  • I have added a comment that contains the name of the application engine step that generated this SQL.  This has can be added automatically with the aeid.sql script on my website.  It can be difficult to identify which step generated which static SQL statement.  It can be impossible to do that with dynamic SQL.  This identifying comment appears in the SQL.
  • I have added a QB_NAME hint to the sub-query, and then the hint can refer to that sub-query (see related blog entry Hinting Sub-Queries on Oracle).
  • Rather than specify the index name in the INDEX hint I have use the table_name(column_list) construction to specify an index on a named table that starts with the named columns.  This is good general practice, the hint remains valid in the case that an index name changes.  However, it is also useful here because there is no meta-data that I can use to construct the name of the index.
#eeeeee; border: 0px solid rgb(0, 0, 0); overflow: auto; padding-left: 4px; padding-right: 4px; width: 100%;">
UPDATE /*+INDEX(@SUB1 ln@SUB1 PS_XXX_SPLT_TA2(process_instance,resource_id))          INDEX(PS_XXX_SPLT_TA1 PS_XXX_SPLT_TA1(process_instance,iu_line_type))*/    /*ID-IU_PROCESSOR.P150.P150-010.S*/     PS_XXX_SPLT_TA1 SET    iu_line_type='U'WHERE iu_line_type='2' AND process_instance=12345678 AND setid_iu='XXXXX' AND ledger_group = 'ACTUALS' AND EXISTS (    SELECT /*+QB_NAME(SUB1)*/ 'X'     FROM PS_XXX_SPLT_TA2 ln    where ln.EMPLID2 = PS_XXX_SPLT_TA1.EMPLID2     and ln.SEQ_NUM = PS_XXX_SPLT_TA1.SEQ_NUM     and ln.BUSINESS_UNIT = PS_XXX_SPLT_TA1.BUSINESS_UNIT     and ln.RESOURCE_ID = PS_XXX_SPLT_TA1.RESOURCE_ID     AND ln.setid_iu = 'XXXXX'    AND ln.ledger_group = 'ACTUALS'     AND ln.process_instance = 12345678     GROUP BY ln.BUSINESS_UNIT_GL , ln.ledger, ln.OPERATING_UNIT, ln.BUSINESS_UNIT, ln.RESOURCE_ID, ln.EMPLID2, ln.SEQ_NUM     HAVING SUM(ln.RESOURCE_AMOUNT) <> 0)

So how did I get those hints into the SQL?

First of all remember that Application Engine doesn't know anything about SQL.  An Application Engine step is just a string of characters that will be submitted to the database.  Any PeopleCode macros are executed as the step is prepared and the resultant string is then set to the database.

The name of the PeopleSoft record being updated is in a variable line_wrk2_rec.  I can introduce the contents of the variable line_wrk2_rec with the %BIND() macro.  Normally a string bind variable is delimited by single quotes because it is used in a function or predicate, but the quotes can be suppressed with the NOQUOTES option.  I can convert the PeopleSoft record name to the database table name with the %Table() PeopleCode macro. 

So, in this example

Code in Application Engine Step Expansion
%BIND(line_wrk_rec) 'XXX_SPLT_TA1'
%BIND(line_wrk_rec,NOQUOTES)) XXX_SPLT_TA1
%Table(%BIND(line_wrk_rec,NOQUOTES)) PS_XXX_SPLT_TA1

Note that delivered PeopleSoft SQL never specifies a row source alias on the table being updated because this would be invalid SQL on SQL Server.  Thus one SQL statement can be used on multiple platforms.  Although it is possible to have platform specific steps in Application Engine, PeopleSoft development avoid this wherever possible because it increases their development overheads.  So the row source alias is the table name. 

I have used the expression %Table(%BIND(line_wrk_rec,NOQUOTES)) twice; once for the table alias and then again when I specify the index.  I want to force the use of an index on PS_XXX_SPLT_TA1 that leads on columns PROCESS_INSTANCE and RESOURCE_ID.  This is the code in the Application Engine step that generates the SQL statement above.

#eeeeee; border: 0px solid rgb(0, 0, 0); overflow: auto; padding-left: 4px; padding-right: 4px; width: 100%;">
UPDATE /*+INDEX(@SUB1 ln@SUB1 %Table(%BIND(line_wrk2_rec,NOQUOTES))(process_instance,resource_id))        INDEX(%Table(%BIND(line_wrk_rec,NOQUOTES)) %Table(%BIND(line_wrk_rec,NOQUOTES))(process_instance,iu_line_type))*/    /*ID-IU_PROCESSOR.P150.P150-010.S*/%Table(%BIND(line_wrk_rec,NOQUOTES))  SET iu_line_type='U'  WHERE iu_line_type='2'    AND process_instance=%BIND(process_instance)    AND setid_iu=%BIND(iu_proc_002_aet.setid_ledger)    AND ledger_group = %BIND(iu_proc_002_aet.ledger_group)    AND EXISTS (     SELECT /*+QB_NAME(SUB1)*/ 'X'       FROM %Table(%BIND(line_wrk2_rec,NOQUOTES)) ln         %BIND(iu_where_aet.iu_where_sql,NOQUOTES)%BIND(iu_group_by_aet.iu_group_by_sql,NOQUOTES)         %BIND(iu_proc_002_aet.where_bu,NOQUOTES)        AND ln.setid_iu = %BIND(iu_proc_002_aet.setid_ledger)        AND ln.ledger_group = %BIND(iu_proc_002_aet.ledger_group)        AND ln.process_instance = %ProcessInstance      GROUP BY ln.%BIND(iu_sys_tran_aet.fieldname_bu_gl,NOQUOTES), ln.ledger%BIND(iu_proc_001_aet.iu_group_by_sql,NOQUOTES)      HAVING SUM(ln.%BIND(iu_sys_tran_aet.fieldname_base_amt,NOQUOTES)) <> 0)

There is a problem here (at least there is in theory). If this statement executes for a different table the index hint will instruct the SQL to look for an index on that different table on the same columns.  The predicates in the where clauses are also derived from dynamic code.  If I was being absolutely rigorous, I would have added some procedural code in preceding steps to build this part of the hints dynamically too, however, I am also trying to keep the customisation to a minimum in an area of code that is otherwise vanilla.

I have accepted a compromise.  If the step executes for a different table, the hint will probably be invalid because there is probably no such index on these columns on that table.  There is a risk that such an index does exist and so the hint could be valid but totally inappropriate to the situation because the predicates are totally different.  The result could be very poor performance.  However, in this case, in practice, this risk is zero, and the hint results in appropriate behaviour in all scenarios.  Although this is something that you need to consider on a case by case basis