3.2.7 Storage Modes

MonetDB/SQL supports different storage solutions for restricted application scenarios. They can be triggered by passing '–readonly' and/or '–single-user' command line option to the mserver5 executable. Another solution is to set the environment variables 'gdk_readonly' and 'gdk_single_user' in the mserver5 configuration file ${prefix}/etc/monetdb5.conf to 'yes'.

When working in a regular mode, the query processing spans the basic column storage and the data changed by transactions (inserts, updates, and deletes). For instance, the inserted data, kept in a separate delta structure, are added to the column before other operations in the plan. In a 'read-only mode' modifying transactions are not allowed and the query processing spans only over the basic column storage. One of the consequences is that query execution becomes faster.

The 'single user mode' can be used to pass all updates directly to the persistent tables. It saves the management and re-consolidation of the transaction delta tables.

NOTE. The storage modes should be used with care, as they have global effect.