To begin using OML4R, you first connect to a schema in an Oracle Database instance with the ore.connect function.

Only one OML4R connection can exist at a time during an R session. If an R session is already connected to the database, then invoking ore.connect terminates the active connection before opening a new connection. Before attempting to connect, you can discover whether an active connection exists by using the ore.is.connected function.

You explicitly end a connection with the ore.disconnect function. If you do not invoke ore.disconnect, then the connection is automatically terminated when the R session ends.

Using the connection type ORACLE, you can do the following:

• Use the logical all argument to specify whether OML4R automatically creates an ore.frame object for each table to which the user has access in the schema and makes those ore.frame objects visible in the current R session. The ore.frame objects contain metadata about the tables. The default value of the all argument is FALSE.

  If all = TRUE, then OML4R implicitly invokes the ore.sync and ore.attach functions. If all = FALSE, then the user must explicitly invoke ore.sync to create ore.frame objects. To access these objects by name, the user must invoke ore.attach to include the names in the search path.

• Use either the conn_string argument, or various combinations of the user, sid, host, password, port, service_name, and conn_string arguments to specify information that identifies the connection.

  To avoid using a clear-text password, you can specify an Oracle wallet password with the conn_string argument. No other arguments are needed. By specifying an Oracle wallet password, you can avoid embedding a database user password in application code, batch jobs, or scripts.

  With the other connection identifier arguments, you specify a database user name, host name, and password, and either a system identifier (SID) or service name, and, optionally, a TCP port, or you specify a database user name, password, and a conn_string argument.

  The default value of the port argument is 1521, the default value of host is "localhost", which specifies the local host, and the default value of conn_string is NULL. You specify the local host when your R session is running on the same computer as the Oracle Database instance to which you want to connect.