ASE15.7 optimzer :"log scan"

Hi

we are runing a in-house apps and having performance issues/blockig when runing a showplan I see same table with "Log Scan" what does this means ? , this table has > 10 mil rows

1

The type of query is UPDATE.

5 operator(s) under root

|ROOT:EMIT Operator (VA = 5)

|

| |UPDATE Operator (VA = 4)

| | The update mode is deferred.

| |

| | |NESTED LOOP JOIN Operator (VA = 3) (Join Type: Inner Join)

| | |

| | | |RESTRICT Operator (VA = 1)(0)(0)(0)(4)(0)

| | | |

| | | | |SCAN Operator (VA = 0)

| | | | | FROM TABLE

| | | | | mfs_files

| | | | | d

| | | | | Log Scan.

| | | | | Forward Scan.

| | | | | Positioning at start of table.

| | | | | Using I/O Size 2 Kbytes for data pages.

| | | | | With MRU Buffer Replacement Strategy for data pages.

| | |

| | | |SCAN Operator (VA = 2)

| | | | FROM TABLE

| | | | adMirrorUsage

| | | | m

| | | | Using Clustered Index.

| | | | Index : mirrorID

| | | | Forward Scan.

| | | | Positioning by key.

| | | | Keys are:

| | | | mirrorID ASC

| | | | Using I/O Size 2 Kbytes for index leaf pages.

| | | | With LRU Buffer Replacement Strategy for index leaf pages.

| | | | Using I/O Size 2 Kbytes for data pages.

| | | | With LRU Buffer Replacement Strategy for data pages.

| |

| | TO TABLE

| | adMirrorUsage

| | Using I/O Size 2 Kbytes for data pages.

Total estimated I/O cost for statement 10 (at line 30): 136.

QUERY PLAN FOR STATEMENT 11 (at line 37).

Optimized using Serial Mode

STEP 1

The type of query is UPDATE.

4 operator(s) under root

|ROOT:EMIT Operator (VA = 4)

|

| |UPDATE Operator (VA = 3)

| | The update mode is deferred.

| |

| | |NESTED LOOP JOIN Operator (VA = 2) (Join Type: Inner Join)

| | |

| | | |SCAN Operator (VA = 0)

| | | | FROM TABLE

| | | | mfs_files

| | | | d

| | | | Log Scan.

| | | | Forward Scan.

| | | | Positioning at start of table.

| | | | Using I/O Size 2 Kbytes for data pages.

| | | | With MRU Buffer Replacement Strategy for data pages.

| | |