Slide 32 of 52
Notes:
Wire protocol can be as simple as NFS or SMB file-server protocol - if a Data Access Manager has arranged appropriate permissions.
Things to note are: (1) potentially very large client side cache, so many queries cause no network traffic at all, especially if they are local 'close to' data previously accessed and in the cache, (2) a query that requires examination of all the data has to get all the data from the server! So these architectures sometimes do NOT make a query language available.
Hybrids are possible, e.g. O2 which uses OQL and does have a query processor on the server. More commonly, the indexes are downloaded into the client cache so queries can be processed y the local Object Server, and only matching objects then need to travel over the network. This would be inappropriate for a transaction processing system where indexes are constantly updated, but for long-transaction, check-in/-out operations, it is most efficient.
The key distinctions to understand are (a) long versus short transaction systems and (b) the adjacency of data in successive operations.
