In other words, given a database instance
I, Q(I) is an n-ary relation instance, the answer to the query.
This was not possible earlier as the same database instance
was used by all departments and they had to wait for their turn.
Finally, while most workloads can be supported with a single database instance
, some workloads require multiple database instances
due to increased scalability requirements (e.g., lots of data or lots of concurrent reads and writes).
We can then update any database instance
to the latest master by running the change log of all the changes since we copied the master to produce the older database instance
Additional scope for block size tuning is also provided by Oracle 9i, which allows mixed block sizes in the same database instance
. All of the decisions made about de-normalising and over-normalising in a separate warehouse schema which are taken to optimise query performance and allow an efficient roll out of historical data, are likely to remain valid for a co-resident scheme.
You can add memory, move to a database instance
with higher CPU capacity, pay for provisioned input/output operations per second (IOPS), or move to solid-state disk storage (SSD).
During this process, it's not uncommon to also cloudify some components of a workload, using a CDN, as explained before, or using a database as a service (DBaaS) instead of a full database instance
on a dedicated cloud server.