Function transaction_start

src/jrd/tra.cpp:3509–3809

static void transaction_start(thread_db* tdbb, jrd_tra* trans)
{
/**************************************
 *
 *	t r a n s a c t i o n _ s t a r t
 *
 **************************************
 *
 * Functional description
 *	Start a transaction.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* const dbb = tdbb->getDatabase();
	Jrd::Attachment* const attachment = tdbb->getAttachment();
	WIN window(DB_PAGE_SPACE, -1);

	Lock* lock = FB_NEW_RPT(*tdbb->getDefaultPool(), 0) Lock(tdbb, sizeof(TraNumber), LCK_tra);

	// Read header page and allocate transaction number.  Since
	// the transaction inventory page was initialized to zero, it
	// transaction is automatically marked active.

	TraNumber oldest, number, active, oldest_active;

#ifdef SUPERSERVER_V2
	number = bump_transaction_id(tdbb, &window);
	oldest = dbb->dbb_oldest_transaction;
	active = MAX(dbb->dbb_oldest_active, dbb->dbb_oldest_transaction);
	oldest_active = dbb->dbb_oldest_active;

#else // SUPERSERVER_V2
	if (dbb->readOnly())
	{
		number = dbb->generateTransactionId();
		oldest = dbb->dbb_oldest_transaction;
		oldest_active = dbb->dbb_oldest_active;
	}
	else
	{
		const bool dontWrite = (dbb->dbb_flags & DBB_shared) &&
			(trans->tra_flags & TRA_readonly);

		const header_page* header = bump_transaction_id(tdbb, &window, dontWrite);
		number = Ods::getNT(header);
		oldest = Ods::getOIT(header);
		oldest_active = Ods::getOAT(header);
	}

	// oldest (OIT) > oldest_active (OAT) if OIT was advanced by sweep
	// and no transactions was started after the sweep starts
	active = MAX(oldest_active, oldest);

#endif // SUPERSERVER_V2

	// Allocate pool and transactions block.  Since, by policy,
	// all transactions older than the oldest are either committed
	// or cleaned up, they can be all considered as committed.  To