Function TRA_header_write

src/jrd/tra.cpp:731–796

#ifdef SUPERSERVER_V2
void TRA_header_write(thread_db* tdbb, Database* dbb, TraNumber number)
{
/**************************************
 *
 *	T R A _ h e a d e r _ w r i t e
 *
 **************************************
 *
 * Functional description
 *	Force transaction ID on header to disk.
 *	Do post fetch check of the transaction
 *	ID header write as a concurrent thread
 *	might have written the header page
 *	while blocked on the latch.
 *
 *	The idea is to amortize the cost of
 *	header page I/O across multiple transactions.
 *
 **************************************/
	SET_TDBB(tdbb);

	// If transaction number is already on disk just return.

	if (!number || dbb->dbb_last_header_write < number)
	{
		WIN window(HEADER_PAGE_NUMBER);
		header_page* header = (header_page*) CCH_FETCH(tdbb, &window, LCK_write, pag_header);

		const TraNumber next_transaction = Ods::getNT(header);
		const TraNumber oldest_active = Ods::getOAT(header);
		const TraNumber oldest_transaction = Ods::getOIT(header);
		const TraNumber oldest_snapshot = Ods::getOST(header);

		if (next_transaction)
		{
			if (oldest_active > next_transaction)
				BUGCHECK(266);	//next transaction older than oldest active

			if (oldest_transaction > next_transaction)
				BUGCHECK(267);	// next transaction older than oldest transaction
		}

		// The header page might have been written while waiting
		// for the latch; perform a post fetch check and optimize
		// this case by not writing the page again.

		if (!number || dbb->dbb_last_header_write < number)
		{
			CCH_MARK_MUST_WRITE(tdbb, &window);

			if (dbb->dbb_next_transaction > next_transaction)
				Ods::writeNT(header, dbb->dbb_next_transaction);

			if (dbb->dbb_oldest_active > oldest_active)
				Ods::writeOAT(header, dbb->dbb_oldest_active);

			if (dbb->dbb_oldest_transaction > oldest_transaction)
				Ods::writeOIT(header, dbb->dbb_oldest_transaction);