Question

Is it true that better concurrency can be achieved in Oracle databases than in MS SQL Server databases? In particular in an OLTP scenario, such as an ERP system?

I’ve overheard an SAP consultant making this claim, referring to Oracle locking techniques like row locking and multi-version read consistency and the redo log.

Answer 1

Out of the box, Oracle will have a higher transaction throughput but this is because it defaults to MVCC. SQL Server defaults to blocking selects on uncommitted updates but it can be changed to MVCC as well so that difference should basically go away. See Read Committed Isolation Level.

See Enabling Row Versioning-Based Isolation Levels.

When the ALLOW_SNAPSHOT_ISOLATION
database option is set ON, the
instance of the Microsoft SQL Server
Database Engine does not generate row
versions for modified data until all
active transactions that have modified
data in the database complete. If
there are active modification
transactions, SQL Server sets the
state of the option to PENDING_ON.
After all of the modification
transactions complete, the state of
the option is changed to ON. Users
cannot start a snapshot transaction in
that database until the option is
fully ON. The database passes through
a PENDING_OFF state when the database
administrator sets the
ALLOW_SNAPSHOT_ISOLATION option to
OFF.