Does this mail lists topic say: "MySQL - Answes and question?"
No it does not.... > -----Original Message----- > From: Sviss Cobazor [mailto:[EMAIL PROTECTED]] > Sent: Sunday, April 14, 2002 7:38 PM > To: [EMAIL PROTECTED] > Subject: [PHP-WIN] MySQL-max and transaction isolation level ? > > > Hi NG. > > Can anybody tell me what the possible isolation levels for MySQL-max means > while using BDB tables? > The meaning of each possible isolation level isn't described, only what > levels are possible to set. > > You can start your server with one of the following values: > > transaction-isolation= READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, > SERIALIZABLE > But what does each of these mean? AN isolation level is about how "isolated" and action is in the database. Read uncommitted, or dirty read, is the lowest isolation level in the data base and means that data you just read can be deleted or modified since no locks are hold on data. Hence, your data might or might not be updated, or deleted by some other process. Read committed means that shared locks are held while the data is being read in order to prevent dirty reads, but your data can be changes by other procress before the end of the transaction since this is not an atomic operation. Repeatable read means that locks are placed on all data that is used in the query. But this does not prevent the inserts of phantom rows by other processes. Serializable means just exactly what it says: it prevents concurrency, in the database and perform an holdlock on everything you uses - even with the select statements during the transaction. This is the most isolated form of transaction you can do - and your entire transaction is more or less an atomic operation in the database. > thanks in advance... > > ~ Sviss > > > > > -- > PHP Windows Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > -- PHP Windows Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
