Function dpiPool_acquireConnection 

pub unsafe extern "C" fn dpiPool_acquireConnection(
    pool: *mut dpiPool,
    userName: *const c_char,
    userNameLength: u32,
    password: *const c_char,
    passwordLength: u32,
    createParams: *mut dpiConnCreateParams,
    conn: *mut *mut dpiConn,
) -> c_int

Acquires a connection from the pool and returns a reference to it. This reference should be released by calling dpiConn_release() as soon as it is no longer needed, which will also return the connection back to the pool for subsequent calls to this function. The connection can be returned back to the pool earlier by calling dpiConn_close().

The function returns DPI_SUCCESS for success and DPI_FAILURE for failure.