Saturday, December 19, 2009

MySQL Table corruption post Migration to MySQL5

With the newer versions of MySQL coming into the market, it becomes obvious for the database users to migrate to the new version. Migration primarily allows you to use the additional functionalities of the new version. Few additional functionalities could be increased speed and security. While migration allows you with numerous benefits, it might also result in corruption of database. Once the database is corrupted, it becomes unmountable making its records inaccessible. In such situations, an updated database backup acts as a boon and allows you to restore the database components. However, there are many occasions where the users either forgets to create a database backup or backup falls short to restore the required data. For such scenarios, only an advanced MySQL Repair software can help.

As a practical case, you migrated your MySQL database from MySQL 4.1 to MySQL5. After doing so, when you attempt to access the records stored in your tables, you receive the below error message:

“wikidb.archive1
Error : Table 'wikidb.archive1' doesn't exist
error : Corrupt
wikidb.categorylinks1
Error : Table 'wikidb.categorylinks1' doesn't exist
error : Corrupt
wikidb.externallinks1
Error : Table 'wikidb.externallinks1' doesn't exist
error : Corrupt
wikidb.filearchive1
Error : Table 'wikidb.filearchive1' doesn't exist
error : Corrupt”

The error message clearly indicates corruption of MySQL tables.

Cause:

Migration can result into MySQL database corruption under following circumstances:

Incomplete migration
Compatibility Issues

Resolution:

To resolve the above error message and to access the data stored in tables, you will need to follow the below steps:

1.Check the extent of table corruption using mysqlcheck [options] dbname tablename [tablename2... ] command.
2.Repair the table using repair table tablename [,tablename1...][options] command.

The overhead steps confirm complete repair in most of the table corruption scenarios. However, if the above steps fail to solve the purpose, then you will need to use advanced MySQL Repair application. Such Repair MySQL Database tools use extensive scanning methods to repair corrupt database objects in most cases. Their interactive user interface makes them easy to understand and implement. In addition, these tools neither delete or modify the original data stored in the database.

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