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In-Memory Database

Posted on 2001-08-02
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I have a 3 tier Application. In the middle tier, which is in the form of active X Exe, i want to get data into the middle tier from the database and maintain it in-memory till the exe is being used.
Please suggest how to maintain the data other than disconnected recordsets
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Question by:agl
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Expert Comment

by:nigelrowe
ID: 6344288
Store it in arrays?
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Accepted Solution

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andyclap earned 200 total points
ID: 6344313
Memory databases are extremely powerful when used correctly - I use the concept in my current application and the performance is amazing compared to fetches from the database each time.

I can't really go into too much detail here, as my current app's implementation is very complex, but here are a few general things I've come across with cacheing data in memory:

MTS - state is not maintained, so your data cache tier cannot use MTS.

Data synchronisation across machines - If you have data in memory, and it's changed on one machine, the data needs to be refreshed somehow. I used a mechanism using sockets to broadcast data update messages across all client workstations.

My data layer translates recordsets into collections of objects - it's not the fastest way to do things, but it makes coding against the objects very easy. I wrote a small 'generator' program to produce VB code for the data tier objects, their collection, and the general access/synchronisation code based on a database table.

Microsoft are interested in memory databases - SQL server is scheduled to have some kind of client cacheing in the near future, so it might be worth waiting or trying to find out how it's going to be done before coding your own version.

Garbage collection - Unless your DB is small, don't try and keep everything in memory. Use a garbage collection technique to 'forget' data which is not being used. You can use a reference count (like COM), a proper GC (like .net) or an alternative method (I use a callback interface to check if an object is still being referenced by an active object before removing it from the cache).

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Expert Comment

by:Joebob
ID: 6344603
Just curious, what do you have against disconnected recordsets?
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Expert Comment

by:wsh2
ID: 6344701
<ping>.. Listening
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Author Comment

by:agl
ID: 6344759
Joebob

We have used disconnected recordsets in the application using collections along with it.But performance is hampered as we keep as many as 100000 records at a time in memory and using recordsets we have to scroll through each and every record to get to the one we want to process.
So we want a system where we can use sql queries(select,update,insert,delete) and get records in one shot rather than scrolling through them.



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Expert Comment

by:Joebob
ID: 6344838
Why not use the filter property of the recordset.  With tht filter property, ADO searchs the records for you using the indexes that it retrieved from the database.  I assume the fields you want to search by are indexed fields.  By using disconnected recordsets and this property, you should have a in-memory db with good performance at the same time.

If this still doesn't give you the performance you need, then your only real choice is to convert the records into a sorted list that you can use a binary search on.  But of course you can actually do a binary search on a recordset also by using the move method and specifying the record to jump to.
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by:guidway
ID: 7180502
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by:guidway
ID: 7196297
My following recommended disposition:

Points to andyclap

If you have any comment or objection to the recommendation, please leave it here.

guidway
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by:Netminder
ID: 7199558
Per recommendation, force-accepted.

Netminder
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