From: "Steve Edberg" <[EMAIL PROTECTED]>
Sometimes I see that some tables from my database get corrupted. Why does
this happpen and how can I avoid it?
It is not hard to go and use "repair table" but it seems that in this way
some records could be deleted and this is not ok.
If I want to have a very secure database, can I use MySQL? I hope the
answer won't be that I need to make backups regularily.
You'll have to give us some more information...at least:
* What MySQL version, OS platform, and file system used for database?
I am using MySQL 5, under Fedora Core 4, installed with its default options.
* Does this happen at a regular time, or apparently randomly?
It happends apparently randomly. Sometimes I just see that the programs are
not working. Sometimes I can do some simple queries in the table with
problems (like select count(*) from table_name), and the query works fine,
but only when trying some more complex queries I can find that the table is
corrupt and I need to fix it.
Sometimes after fixing the table no records are deleted, but sometimes one
or more records are deleted after fixing it.
* Does this happen to the same tables all the time, or is that random as
well?
I found that it happends in more tables, but especially with one of them.
That table has more than 2 million records and it is a MyISAM table. Should
I use InnoDB instead? (Or another storage system?)
That table is updated by a single program which runs continuously a few
hours every day, and the program add (just addings and no updates)
aproximately 10000 records in those few hours... so they are not very very
many.
But other programs query that table very often.
* Is this a precompiled binary from MySQL or did you build it yourself?
It is a precompiled version from MySQL.
I could see that if you compiled it yourself against some buggy libraries
you could have problems; perhaps a cronjob is doing some copy/restore
process on the underlying files without shutting mysql down or flushing
logs; perhaps a lot of things...more information is needed.
I have also seen (in most of the tables if not all) that after using "check
table table_name" for the first time, I receive the message that the table
was not closed by a few processes (from 2 to 6 processes). If I use that
query a second time, I receive the message that the table is ok, and that
message doesn't appear again.
It has been my experience (on Windows NT, Solaris and Linux platforms)
that MySQL has been one of the more reliable programs out there. Even
after system crashes I haven't lost any data; a repair table and index
rebuild fixed things.
Yes in some cases it is the same for me, but after reparing a table,
sometimes it tells me that some records were deleted because before that
repair query the number of records reported is bigger.
steve
Thank you.
Octavian
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