Long field manager log records

Long field manager log records are written only if a database is recoverable. That is, if the database is configured with either the logarchmeth1 or logarchmeth2 parameter set to a value other than OFF. The log records are written whenever long field data is inserted, deleted, or updated.

To conserve log space, long field data inserted into tables is not logged if the database is configured for circular logging. In addition, when a long field value is updated, the before image is shadowed and not logged.

All long field manager log records begin with a header.

All long field manager log record offsets are from the end of the log manager log record header.

When a table was altered to capture LONG VARCHAR OR LONG VARGRAPHIC columns by specifying INCLUDE LONGVAR COLUMNS on the ALTER TABLE statement:
  • The long field manager writes the appropriate long field log record.
  • When long field data is updated, the update is treated as a delete of the old long field value, followed by an insert of the new value. To determine whether a delete or add long field record is associated with an update operation on the table the original operation value would be logged to the long field manager log record.
  • When tables with long field columns are updated, but the long field columns themselves are not updated, a non-update long field record is written.
  • The delete long field record and the non-update long field record are information only log records.
Table 1. Long field manager log record header (LongFieldLogRecordHeader)
Description Type Offset (Bytes)
Originator code (component identifier = 3) unsigned char 0 (1)
Operation type (See Table 2.) unsigned char 1 (1)
Table space identifier unsigned short 2 (2)
Object identifier unsigned short 4 (2)
Parent table space identifier1 unsigned short 6 (2)
Parent object identifier2 unsigned short 8 (2)
Total Length: 10 bytes
Note:
  1. Table space ID of the data object
  2. Object ID of the data object
Table 2. Long field manager log record header operation type values and definitions
Value Definition
113 Add long field record
114 Delete long field record
115 Non-update long field record

Add/delete/non-update long field record log records

These log records are written whenever long field data is inserted, deleted, or updated. The length of the data is rounded up to the next 512-byte boundary.

Table 3. Add/Delete/Non-update long field record log record structure
Description Type Offset (Bytes)
Log header LongFieldLogRecordHeader 0 (10)
Internal Internal 10 (1)
Original operation type1 char 11 (1)
Column identifier2 unsigned short 12 (2)
Long field length3 unsigned short 14 (2)
File offset4 sqluint32 16 (4)
Long field data char[ ] 20 (variable)
Note:
  1. Original operation type 
      1     Insert
  2     Delete
  4     Update
  2. The column number that the log record is applied to. Column number starts from 0.
  3. Long field data length in 512-byte sectors (actual data length is recorded as the first 4 bytes of long field descriptor (LF descriptor), which is logged in the following insert/delete/update log record as part of formatted user data record). The value of this field is always positive.

    The long field manager never writes log records for zero length long field data that is being inserted, deleted, or updated.

  4. 512-byte sector offset into long field object where data is to be located.