Data Manipulation Language (DML) operations include insertions, deletions, updates, and queries. For all such operations, Sybase IQ permits one writer and multiple readers on any given table. This rule has the following implications:
Read transactions do not block write transactions.
Write transactions do not block read transactions.
A single update user and multiple read-only users can concurrently access a table.
Only a single user can update the data in a given table at one time.
The first transaction to open a table in write mode gains access to the table. A second transaction that tries to open the table in write mode receives an error. Any additional attempts to write to the table in the current transaction will fail. The transaction can continue, but only with read operations or with writes to other tables.
