Why there are 2 separate pools: VCS Pool and DB Pool ?

[Ankush_Bandil]

I have few questions regarding VCS and DB Pool.

1. Why there are different pools called VCS Pool and DB Pool?
2. What is the purpose of each pool?
3. Does VCS pool consume the connection of the database?

[Florent_Guillau · Accepted solution]

In general the notion of pool exists to collect pre-allocated resources which are expensive to re-create.

In Nuxeo we use a "db" pool for JDBC connections, which are expensive to recreate because they trigger network access and take time to execute in the SQL server.

And we use a "vcs" pool for low-level Nuxeo sessions, which are expensive to recreate because they hold a cache of already-fetched objects which is itself expensive to re-create.

And yes each time you use a Nuxeo session you have to take a session from the "vcs" pool, and also take a connection from the "db" pool.