Virtual Memory and Databases

The Solaris Resource Manager product also provides the capability to limit the amount of virtual memory used by users and workloads. This capability does not manage physical memory; rather it effectively restricts the amount of global swap space that is consumed by each user.

When a user or workload reaches the virtual memory limit set for their lnode, the system returns a memory allocation error to the application; that is, calls to malloc() fail. This error code is reported to the application as though the application had run out of swap space.

Few applications respond well to memory allocation errors. Thus, it is risky to ever let a database server reach its virtual memory limit. In the event that the limit is reached, the database engine might crash, resulting in a corrupted database.

Virtual memory limits should be set high so they are not reached under normal circumstances. Additionally, the virtual memory limit can be used to place a ceiling over the entire database server, which will stop a failing database with a memory leak from affecting other databases or workloads on the system.