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Oracle In-Memory Option: 6 Key Points
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bhall2
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bhall2,
User Rank: Apprentice
6/19/2014 | 12:37:46 PM
Re: In-memory and indexes, a question.....
Charlie,

Yes apps create indexes on tables/partitions to speed up access to rows based on queries against column(s). Without that index it may have to do a full table scan instead (slow for large tables). And yes, an application can submit SQL with a hint (for very specific cases) specifying the optimizer to use a certain index. However, that has and always will be a - hint - not an absolute.

So when you drop the index on that column and instead tell oracle to load it into memory, the optimizer will now ignore your hint if you had one (which it may have before anyhow) and just use the faster columnar memory copy instead (when it makes sense).

So no changes beyond dropping the index and telling the database to cache the column instead. This is what newer versions of apps (the "changes") will do. When it makes sense a new version will go drop all the indexes, and tell Oracle to cache. Not exactly tricky - other than to do it in a smart order that makes sense based on how much memory you have available for the column cache.

Bryan
philweir
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philweir,
User Rank: Apprentice
6/13/2014 | 3:57:10 PM
Re: All-in-memory versus not: mixed storage is winning
SAP is not positioning an 'all-in-memory" approach. Its position is to use lower cost storage for warm data and DRAM for hot data.  Unfortunately, the definition of Hot and Warm is different by user.  The term 'center' must mean the data modelling application in your context, which Hana is more than capable of doing but does not require all the data be in-memory to do so.  Are you saying the center is the database? 
D. Henschen
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D. Henschen,
User Rank: Author
6/13/2014 | 3:22:03 PM
Re: All-in-memory versus not: mixed storage is winning
Or course it's possible for Hana or another in-memory database to tap into information from other systems, but are you going to retain all that information in-memory. And if not, will you get in-memory performance? SAP's assertion that you can get rid of the data warehouse assumes that SAP is the center your DW universe. Also assumes you don't have a lot of history or are prepared to spend a lot of money on DRAM to ratain it all.
philweir
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philweir,
User Rank: Apprentice
6/13/2014 | 2:32:22 PM
Re: All-in-memory versus not: mixed storage is winning
Dan - you make two points which are relevant.  First the 'work' to do is done by the software vendors.  Which means the database/ in-memory speeds are possible but only with the application vendors using it.  That is what SAP is doing and others are not.  SAP ignited this technology discussion because its applications were being slowed by the db providers.  It took responsible for the solution used by the users and removed the constraint causing the issue.  Further it is reinvesting in the applications to allow them to take advantage of the speed.   Second, your inclusion of larry's suggestion that it wont work with data not coming from SAP puts you in the position of saying that data warehousing would never had worked because by definition they are taking in data from other sources.   The real point is that the design of data warehouse was flawed because of rigidity, which is reduced within in memory and with the speed creates the justification over this band-aiding of 1980s technology.   
D. Henschen
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D. Henschen,
User Rank: Author
6/13/2014 | 9:58:36 AM
Re: In-memory and indexes, a question.....
Not quite. In this case they're talking about analytical (columnar) indexes, but because columns are now available in memory, Oracle is saying you can get rid of them because the in-memory store is so fast. SAP makes similar claims (about all indexes). Whether that can be done "without disruption" is another matter. If an app is looking for/dependent upon an index that's removed, is may not work properly. Oracle is saying it's DBMS optimizer has been trained to reinterpret the index call agains the in-memory store, but there's no assurance that will work in every case.
Charlie Babcock
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Charlie Babcock,
User Rank: Author
6/12/2014 | 8:50:10 PM
In-memory and indexes, a question.....
I thought specific applications worked with specific indexes that the application, in an early pass, prompted the database system to build through its query patterns. By getting rid of indexes, Oracle must mean they get rid of them temporarily for purposes of in-memory operations? Restore them afterward for routine operations? 
D. Henschen
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D. Henschen,
User Rank: Author
6/11/2014 | 1:02:19 PM
All-in-memory versus not: mixed storage is winning
Oracle, like Microsoft, may have an edge over all-in-memory purists, like SAP, when it comes to popular sentiment. Yes, the all-in-memory route means there will be no compromises when it comes to performance and data exploration. But even in-memory advocates in the analytics space like MemSQL and VoltDB recognize that there's a need for warm and cool data stored on less-expensive options like Flash and Disk. I've talked to SAP customers who aren't so sure they can get rid of data warehouses because they have lots of historical data or because not everything they do runs inside of SAP.

Oracle CEO Larry Ellison argued "why not put the hot data in memory and leave everything else in flash or disk?" I think that makes sense to many, and with dynamic, intelligent hot/warm/cold loading and data movement (still to come in this in-memory offering) it's possible to get most of the performance gain you need without breaking the bank. SAP would argue that it can size down the total data footprint by storing data only once in a compressed, columnar, in-memory form and drive all uses. But what about historical data or data not flowing from SAP? People know what they have today and just see big dollar signs when they think of putting it all in RAM.


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