tag:blogger.com,1999:blog-4096575.post6249498792221612474..comments2024-03-28T07:44:02.549-04:00Comments on The Arup Nanda Blog: Can I Fit a 80MB Database Completely in a 80MB Buffer Cache?Arup Nandahttp://www.blogger.com/profile/03392706779349258765noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-4096575.post-29279070006584898902012-06-06T05:03:50.856-04:002012-06-06T05:03:50.856-04:00I searched a long time for such an great article. ...I searched a long time for such an great article. Thank you very much.<br /><a href="http://www.diskdoctors.com/software/digital-media-recovery/utility.asp" rel="nofollow">disk doctors digital media recovery</a>Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4096575.post-40366671168309115082011-06-27T06:44:29.276-04:002011-06-27T06:44:29.276-04:00Great article. Neatly explained.
Many thanks to yo...Great article. Neatly explained.<br />Many thanks to you.Nitin Rhttps://www.blogger.com/profile/03916592287972550741noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-90511188214614199102011-06-07T00:56:10.214-04:002011-06-07T00:56:10.214-04:00very good post........
all d bestvery good post........<br /><br />all d bestNEERAJ VISHENhttps://www.blogger.com/profile/04032578930084182369noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-55779172741019011702011-04-27T03:23:57.313-04:002011-04-27T03:23:57.313-04:00Quote:
The CR processing creates copies of the buf...Quote:<br /><i>The CR processing creates copies of the buffer and rolls them back <b>or forward</b> to create the CR copy as of the correct SCN number.</i><br /><br />Could you expand a bit on that? I can see how a buffer may be rolled back (by aplying undo), but forward? That would require redo, which is a whole different can of worms.<br /><br />Cheers,<br />FladoFladohttps://www.blogger.com/profile/04901763101139511192noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-64433338010216051292011-04-18T10:20:16.072-04:002011-04-18T10:20:16.072-04:00Great article Arup, we already attend the next one...Great article Arup, we already attend the next one...Albertohttps://www.blogger.com/profile/01805632595255042258noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-3833148356414892802011-04-18T09:21:19.205-04:002011-04-18T09:21:19.205-04:00Excellent illustration. I logged in to an Oracle s...Excellent illustration. I logged in to an Oracle session and typed in the examples as I read. <br /><br />It's interesting to see how many people think having a large SGA means the entire database is in memory. Even if that was possible, in order to do that the application must select all rows from all tables and indexes which is not realistic.<br /><br />Additionally, just because a row was loaded in the buffer cache doesn't mean it will stay there indefinitely so at some point in the future the same row would have to be read from disk again.<br /><br />This brings me to another question: If a row is loaded in the buffer cache and later the buffer is marked free will Oracle reuse that buffer or will it allocate a new one (assuming there is a lot of free, unallocated memory)? I'm just trying to understand if Oracle continues to consume or allocate memory even if there are free buffers that could be reused. Would that only happen if it's running low on memory? <br /><br />ThanksEnrique Avilesnoreply@blogger.comtag:blogger.com,1999:blog-4096575.post-75150548165694505752011-04-17T21:23:33.121-04:002011-04-17T21:23:33.121-04:00This is indeed interesting!...Thanks for sharing t...This is indeed interesting!...Thanks for sharing this!...Danielpainting techniqueshttp://www.oilpaintingworkshop.comnoreply@blogger.comtag:blogger.com,1999:blog-4096575.post-26114039732501793942011-04-17T21:20:26.806-04:002011-04-17T21:20:26.806-04:00@Surachart - thank you.@Surachart - thank you.Arup Nandahttps://www.blogger.com/profile/03392706779349258765noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-7060087716700713222011-04-17T21:20:11.426-04:002011-04-17T21:20:11.426-04:00@MWF - thanks for chiming in. One of the most comm...@MWF - thanks for chiming in. One of the most common myths folks tend to dabble in is that a table defined as cached (alter table xxx cache) is cached. In a future blog in this series I hope to bust that myth.Arup Nandahttps://www.blogger.com/profile/03392706779349258765noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-7982234124319330252011-04-17T21:18:18.873-04:002011-04-17T21:18:18.873-04:00@Bryan - your point is exactly what I was trying t...@Bryan - your point is exactly what I was trying to illustrate. Oracle' buffer cache mechanism does not allow entire database to fit into the buffer cache. If a all-memory access is desired, the best choice is to get a database specifically designed for that purpose, e.g. TimesTen.<br /><br />In part 2 of this topic I am going to explain how you can accomplish the objective of most of the buffers of the block.Arup Nandahttps://www.blogger.com/profile/03392706779349258765noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-33512081546702292282011-04-17T02:49:50.292-04:002011-04-17T02:49:50.292-04:00Nice work Arup! And it reminds me to remind custom...Nice work Arup! And it reminds me to remind customers to consider this when intending to place volatile objects in keep cache they cannot budget merely the size of the object in question. Measurements over time are required to have enough head room to avoid most thrashing.<br /><br />mwf@rsiz.com (anon for not logging in)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4096575.post-82450903625159313952011-04-17T00:05:56.987-04:002011-04-17T00:05:56.987-04:00Very nice article Arup. I have been giving this co...Very nice article Arup. I have been giving this concept a lot of thought. We have been meeting with hardware vendors that are promising 4tb of memory in the next couple of years. Of course your topic has come to mind. Can you fit the whole database in memory ? What does this mean to our future Storage decisions ? <br />I am going to look closely at your block usage testing (and include some index block testing since we have a lot of indexes), to see how big of a database we can fit into 4tb of memory. From the looks of your testing, if there are lots of updates, we might find a 1tb database might not even fit. I certainly didn't expect that !Bryan Grennhttps://www.blogger.com/profile/04007049262897217651noreply@blogger.comtag:blogger.com,1999:blog-4096575.post-31224551414643561962011-04-16T23:34:37.057-04:002011-04-16T23:34:37.057-04:00Great -)
Thank YouGreat -) <br />Thank YouSurachart Opunhttps://www.blogger.com/profile/05646896104906516714noreply@blogger.com