Set decimal 1GB default LOB prefetch

src/main/java/oracle/r2dbc/impl/OracleReactiveJdbcAdapter.java

@@ -648,15 +648,13 @@ private static void configureJdbcDefaults(OracleDataSource oracleDataSource) {
     setPropertyIfAbsent(oracleDataSource,
       OracleConnection.CONNECTION_PROPERTY_IMPLICIT_STATEMENT_CACHE_SIZE, "25");
 
-    // Prefetch LOB values by default. The database's maximum supported
-    // prefetch size, 1GB, is configured by default. This is done so that
-    // Row.get(...) can map LOB values into ByteBuffer/String without a
-    // blocking database call. If the entire value is prefetched, then JDBC
-    // won't need to fetch the remainder from the database when the entire is
-    // value requested as a ByteBuffer or String.
+    // Prefetch LOB values by default. This allows Row.get(...) to map most LOB
+    // values into ByteBuffer/String without a blocking database call to fetch
+    // the remaining bytes. 1GB is configured by default, as this is close to
+    // the maximum allowed by the Autonomous Database service.
     setPropertyIfAbsent(oracleDataSource,
       OracleConnection.CONNECTION_PROPERTY_DEFAULT_LOB_PREFETCH_SIZE,
-      "1073741824");
+      "1000000000");
 
     // TODO: Disable the result set cache? This is needed to support the
     //  SERIALIZABLE isolation level, which requires result set caching to be

src/test/java/oracle/r2dbc/impl/OracleLargeObjectsTest.java

@@ -729,9 +729,8 @@ public void run() {
             + " PRIMARY KEY(id))"));
 
         // Insert two rows of LOBs larger than 1MB
-        byte[] bytes = new byte[lobSize];
+        byte[] bytes = getBytes(lobSize);
         ByteBuffer blobValue = ByteBuffer.wrap(bytes);
-        Arrays.fill(bytes, (byte)'a');
         String clobValue = new String(bytes, US_ASCII);
         awaitUpdate(List.of(1,1), connection.createStatement(
           "INSERT INTO testLobPrefetch (blobValue, clobValue)"