## Example: Error in the Data Structure

A base table contains a defective data page on the leaf level of the B* tree of the base table: leaf number 44690 with block address 1/564.

During a check of the database structure, the database system notices that the checksum for the data page is incorrect. The database system writes the following information in the kernel log (see Log Files):

● Error in the checksum

● Page number with data volume and block address information.

● Page number in the B* tree

● Type of the database object represented by the B* tree

● Root page of the B* tree

● Error message

Then the database system internally marks the database object as BAD.

#### Excerpt from the Kernel Log

2005-04-08 09:40:28 0xCEC ERR 4 Data Data_BasePage.cpp:124

2005-04-08 09:40:28 0xCEC ERR 4 Data 2005-04-08 09:40:28 AM Data Error 4

2005-04-08 09:40:28 0xCEC ERR 4 Data Checksum mismatch; calculated: 5468846 found: 22246062

2005-04-08 09:40:28 0xCEC ERR 25 IOMan IOMan_Volume.cpp:500

2005-04-08 09:40:28 0xCEC ERR 25 IOMan 2005-04-08 09:40:28 AM IOMan Error 25

2005-04-08 09:40:28 0xCEC ERR 25 IOMan Bad page on Data volume 1 blockno 564

2005-04-08 09:40:30 0xCEC ERR 36 IOMan IOMan_Manager.cpp:1007

2005-04-08 09:40:30 0xCEC ERR 36 IOMan 2005-04-08 09:40:30 AM IOMan Error 36

2005-04-08 09:40:30 0xCEC ERR 36 IOMan Bad data page 44690

2005-04-08 09:40:30 0xCEC ERR 18 Data vbd13.cpp:2426

2005-04-08 09:40:30 0xCEC ERR 18 Data 2005-04-08 09:40:30 AM Data Error 18

2005-04-08 09:40:30 0xCEC ERR 18 Data Bad data page 44690 of filetype 'Table' identified by root 104236

2005-04-08 09:40:30 0xCEC ERR 53021 B*TREE Bad File: 104236 (Root)

2005-04-08 09:40:30 0xCEC ERR 53000 B*TREE 0D000000000000000388000000000000

2005-04-08 09:40:30 0xCEC ERR 53000 B*TREE Table Root 104236

2005-04-08 09:40:30 0x37C ERR 53019 CHECK Base error: bad_datapage

2005-04-08 09:40:30 0x37C ERR 53019 CHECK Root pageNo: 104236

See also:

Checking Database Structures

Logical Access Structures