distributed concurrency in oracle 7.0

Hi!
Can someone tell me how oracle scheduler maintains the concurrency? The only thing I could get from the product info was that it uses multiversion data items and does not require any read locks. I am sort of confused. I have a background of concurrency control including Multiversion TO, Multiversion 2PL,... . I will be thankful if somene could put some light. and It seems the scheduler does not provide serializability by default. I need to know about that also. In this respect, I read a paper titled "Single-Level Multiversion Schedulers for Multilevel Secure Database Systems". This paper discusses scheduler algorithms implemented for Trusted Oracle. The first author of this paper is Mr. William T. Maimone of Oracle Corportaion. Somewhere, this paper says that standard Oracle product provides read-consistency but does not provide repeatable reads that makes its default locking strategy different from serializability. Well, I didn't understand properly because I don't know how Oracle's default locking strategy works. However, it further says that in terms of serializability, the behavior of Oracle is quite similar to that of other commercial DBMS products. So, does that mean that most of the commercial DBMS products sacrifice serializability? Could somebody give me some examples? Thanks a lot.
sameer Received on Tue Jul 20 1993 - 03:17:20 CEST