Shared Memory Connections

Shared Memory Connections

InterSystems IRIS uses a shared memory connection rather than TCP/IP when a Java application is running on the same machine as an InterSystems IRIS server instance. This section explains how shared memory works, and how to disable it for development and testing purposes.

Shared memory connections maximize performance by avoiding potentially expensive calls into the kernel network stack, thus providing optimal low latency and high throughput for JDBC operations.

If a connection specifies server address localhost or 127.0.0.1, shared memory will be used by default. TCP/IP will be used if the actual machine address is specified. The connection will automatically fall back to TCP/IP if the shared memory device fails or is not available.

Shared memory can be disabled in the connection string by setting the SharedMemory property to false. The following example creates a connection that will not use shared memory even though the server address is specified as 127.0.0.1:

  Properties props = new Properties();
  props.setProperty("SharedMemory", "false");
  props.setProperty("user", "_system");
  props.setProperty("password", "SYS");
  IRISConnection conn = (IRISConnection)DriverManager.getConnection("jdbc:IRIS://127.0.0.1:1972/USER/ ",props);

Accessors DataSource.getSharedMemory() and DataSource.setSharedMemory() can be used to read and set the current connection mode. The IRISConnection.isUsingSharedMemory() method can also be used to test the connection mode.

Shared memory is not used for TLS or Kerberos connections. The JDBC log will include information on whether a shared memory connection was attempted and if it was successful (see “JDBC Logging”).