SPATIAL DATABASES

SDBMS mjust provide simultaneous, or concurrent, access by multiple user programs to a shared database.

A execution of auser program can be seen as a sequence of read and write operations,which may be interleaved but under a constraint that a logical partial order or serialization between transtions is maintened.

Two basic rules define a locking protocol for concurrency control:

- For a read action on an object, a transaction acquires a shared lock on the object. An exclusive lock is provided for a write action.

- All locks associated with a transaction are released when the transaction is completed.

These rules are adjusted to handle specific components of the indexing structure in operations of inserting and deleting.

 

---