Re: Transactions ISOLATIONS level

From: fumi <fumi_at_tpts5.seed.net.tw>
Date: Thu, 28 Jun 2001 16:24:15 +0800
Message-ID: <9hfkhm$f68$8@news.seed.net.tw>

"Francesco Marchioni" <fmarchioni_at_libero.it> ¼¶¼g©ó¶l¥ó news:jSl_6.5944$363.259102_at_news.infostrada.it...
> Hi all,
> I'm studying transactions isolation levels.
> I have some questions, hope somebody will help me:
>
> 1) How can I change the transaction isolation level via SQL - PL/SQL ?
> ( I mean without administrator's tools)

Oracle supports only SERIALIZABLE and READ COMMITTED. Use the SQL command:

ALTER SESSION SET ISOLATION_LEVEL= {SERIALIZABLE | READ COMMITTED} By the way, I think no tools support this rare used statement.

> 2) When I issue a SELECT FOR UPDATE the transaction level switches
> automatically to TRANSACTIONS_SERIALIZABLE ?

No, after you issue a SELECT FOR UPDATE command, you still in (default) READ COMMITTED level.

> 3) I understand row locking and table locking but what does it mean "page"
> locking ??

Oracle doesn't use page lock.
Page lock means that if you locks one or more rows in a page (block), then all rows in the page (block) are locked. Received on Thu Jun 28 2001 - 03:24:15 CDT