MS Access 2010: “Cannot open any more databases.”

Question

While struggling with a single legacy MS Access application I faced this weird error:

Cannot open any more databases.

The application makes

Answer 1

You need to evaluate each section of your UNION query, and any other queries that it depends upon. You may get improvement by creating a temp table that represents a query with many joined tables, and use the temp table instead.

When I started developing with Access I had a habit of making big denormalized snowflake queries and using them as a source for a reports and listboxes. I didn't have any tables with more than 100,000 records and the database ran fast. Later I started to get the annoying "Cannot open any more databases" error and discovered the errors of my ways.

I created a form that will help track how many databases connections you have used and how many remain. If you add this form to your database and click Requery after opening your queries and other objects, you will be able to find the objects that are using a significant number of connections.

Note that every reference to a local table or query object uses 1 connection. A reference to a linked table uses 2 connections. A query that joins two linked tables will use 5 connections. If that query is getting called by many other queries in your union, the number adds up fast. Maybe you don't need any of the fields from a joined table in a subquery. In that case you can make a new query.

I read a lot about this online and some people think Access/Jet has around 2,000 TableID’s but that number doesn’t match up with what my form reports. The numbers reported by my form align perfectly with the error. It may be counting something different than TableID’s but it provides an accurate gauge to measure the amount of connections being used as you open new objects.

You can read more and download it from here:

https://access.wordpress.com/2014/04/01/how-many-database-connections-are-still-available-in-an-access-database/