Basic ways to optimize this query? - oracle

Question

title pretty much says it all. I wrote this big, ugly query that works...however it takes forever to run. I have no experience whatsoever with optimizing SQL, and am pretty new to the language and its functions. I realize none of you will be familiar with the environment I am working in, but I was just wondering if any basic things jump out at you about it. Thanks!
SELECT MAX(INVOICE.invoice_id) invoice_id, MAX(invoice.vendor_num) vendor_num, max(invoice.vendor_name) vendor_name,
MAX(invoice.po_number) po_number, MAX(invoice.invoice_date) invoice_date, MAX(invoice.invoice_num) invoice_num,
MAX(invoice.terms_name) terms_name, MAX(invoice.invoice_amount) invoice_amount, MAX(invoice.amount_applicable_to_discount) amount_applicable_to_discount,
MAX(invoice.amount_paid) amount_paid, MAX(invoice.payment_date) payment_date, MAX(invoice.document_id) document_id,
MAX(invoice.filename) filename,
STAMPS.page_markups_view_id, STAMPS.TEXT, STAMPS.TOOL_NAME
FROM
(SELECT DISTINCT inv.invoice_id,
vendor.segment1 vendor_num,
vendor.vendor_name,
MAX(poh.segment1) po_number,
inv.invoice_date,
inv.invoice_num,
terms.name terms_name,
inv.invoice_amount,
inv.amount_applicable_to_discount,
inv.amount_paid,
pmt.check_date payment_date,
path.document_id,
vendor.segment1 || '-' || inv.invoice_num || '.pdf' filename
FROM apps.ap_invoices_all inv,
apps.ap_invoice_distributions_all dist,
apps.po_distributions_all podi,
apps.ap_invoice_payment_history_v pmt,
apps.fnd_attached_docs_form_vl fnd,
markview.mv_page_image_paths path,
apps.po_vendors vendor,
apps.po_headers_all poh,
apps.ap_terms terms
WHERE inv.invoice_id = to_number(fnd.pk1_value)
AND inv.invoice_id = dist.invoice_id
AND poh.po_header_id(+) = podi.po_header_id
AND podi.po_distribution_id(+) = dist.po_distribution_id
AND fnd.file_name = to_char(path.document_id)
AND inv.invoice_id = pmt.invoice_id
AND fnd.category_description = 'MarkView Document'
AND fnd.entity_name = 'AP_INVOICES'
AND inv.vendor_id = poh.vendor_id(+)
AND inv.terms_id = terms.term_id
AND inv.vendor_id = vendor.vendor_id
AND path.platform_name = 'UNIX_FS_TO_DOC_SERVER'
AND pmt.void = 'N'
and inv.invoice_id = 1908784
GROUP BY
inv.invoice_id,
vendor.segment1 ,
vendor.vendor_name,
inv.invoice_date,
inv.invoice_num,
terms.name ,
inv.invoice_amount,
inv.amount_applicable_to_discount,
inv.amount_paid,
path.document_id,
pmt.check_date,
vendor.segment1 || '-' || inv.invoice_num || '.pdf'
) INVOICE,
( SELECT mp.document_id,
moi.markup_object_id,
moi.page_markups_view_id,
moi.text,
mvt.tool_name,
mp.page_id
FROM markview.mv_markup_object moi,
markview.mv_tool mvt,
markview.mv_page_markups_view mpmv,
markview.mv_page mp
WHERE moi.tool_id = mvt.tool_id
AND mp.page_id = mpmv.page_id
AND mpmv.page_markups_view_id = moi.page_markups_view_id
AND mvt.tool_id IN
(
SELECT mvt.tool_id
FROM markview.mv_tool
WHERE mvt.tool_name IN ( 'Green Text',
'Blue Sticky Note' ) )) STAMPS
WHERE invoice.document_id = stamps.document_id(+)
GROUP BY
page_markups_view_id, TEXT, TOOL_NAME
)