What Oracle SQL syntax do I need to find transactions that occurred during time intervals of a day for a period of a year

Firstly, I will say that this workload is by no means heavy by Oracle standards; thousands of commits/sec are possible, easily. Secondly, however, what matters here is not your database and it's not your server: it's your storage. There are many options here; you won't go too wrong with something like NetApp (I don't work for them, just a satisfied user) and the question is, what size? Here ORION is your friend. Whatever storage array you choose, this will take care of your first level of resilience, if your first node fails you simply mount the disks on another and start back up again, and Oracle will perform crash recovery so no data will be lost.

My advice is, get some numbers at a lower level - MB/s, IOPs - by performing a representative benchmark and take those to your nearest storage vendor and ask them what they've got. With NetApp at least, you can start fairly small and grow, adding another head for more resilience/better performance, adding shelves for more capacity, etc etc. Then test the crap out of it with Orion!

_{Community wiki answer initially based on comments left by thatjeffsmith:}

This is an exhaustive list of what it supports:

(reproduced from http://pldoc.sourceforge.net/maven-site/samples/sample1.sql)

CREATE OR REPLACE
PACKAGE CUSTOMER_DATA
IS
/** 
* Project:         Test Project (<a href="http://pldoc.sourceforge.net">PLDoc</a>)<br/>
* Description:     Customer Data Management<br/>
* DB impact:       YES<br/>
* Commit inside:   NO<br/>
* Rollback inside: NO<br/>
* @headcom
*/

/**
* Record of customer data.
*
* @param id     customer ID
* @param name       customer name
* @param regno      registration number or SSN
* @param language   preferred language
*/
TYPE customer_type IS RECORD (
  id                        VARCHAR2(20),
  name                      VARCHAR2(100),
  regno                     VARCHAR2(50),
  language                  VARCHAR2(10)
);

/** Table of customer records. */
TYPE customer_table IS TABLE OF customer_type INDEX BY BINARY_INTEGER;

/**
* Gets customer by ID.
*
* @param p_id       customer ID
* @param r          record of customer data
* @throws no_data_found if no such customer exists
*/
PROCEDURE get_customer (
  p_id              VARCHAR2,
  customer_rec      OUT customer_type);

/**
* Searches customer by criteria.
*
* @param p_criteria record with assigned search criteria
* @param r_records  table of found customers <b>(may be empty!)</b>
*/
PROCEDURE get_by_criteria (
  p_criteria        customer_type,
  r_records         OUT customer_table);

/**
* Creates a customer record.
*
* @param customer_rec record of customer data
*/
PROCEDURE create_customer (
  customer_rec      customer_type);

/**
* Changes customer data.
*
* @param customer_rec record of updated customer data
*/
PROCEDURE update_customer (
  customer_rec      customer_type);

END;
/

We support everything in PLDOC - we just have a GUI vs a CLI for it. There are three code samples there, you should be able to do anything listed in those samples.