overflows : interpretation

[hikums]

I have taken a table snapshot, and noticed two tables with high
overflows. What should be done, if any.

Table Schema = CASTING
Table Name = ABC
Table Type = User
Data Object Pages = 309
Index Object Pages = 56
Rows Read = Not Collected
Rows Written = 1368
Overflows = 62310058
Page Reorgs = 236

Table Schema = CLAIMS
Table Name = CLAIMWORK
Table Type = User
Data Object Pages = 3118
Index Object Pages = 1932
Rows Read = Not Collected
Rows Written = 22408
Overflows = 128472
Page Reorgs = 2994

Table Schema = SYSIBM
Table Name = SYSPLANDEP
Table Type = Catalog
Data Object Pages = 23
Index Object Pages = 33
LOB Object pages = 64
Rows Read = Not Collected
Rows Written = 128
Overflows = 1
Page Reorgs = 10

[Anton Versteeg via DBMonster.com]

hi****@gmail.com wrote:

I have taken a table snapshot, and noticed two tables with high
overflows. What should be done, if any.

From the System Monitor Guide:

Description: The number of accesses (reads and writes) to overflowed rows of
this table.

Usage: Overflowed rows indicate that data fragmentation has occurred. If this
number is high, you may be able to improve table performance by reorganizing
the table using the REORG utility, which cleans up this fragmentation. A row
overflows if it is updated and no longer fits in the data page where it was
originally written. This usually happens as a result of an update of a
VARCHAR or an ALTER TABLE statement.
--
Message posted via http://www.dbmonster.com

[Pierre Saint-Jacques]

The only way to get things right will be to REORG the table.
REORG will get the overflow caused by the VARCHAR length increase to be
restructured and will then get rid of the overflowed row.
If the overflows are caused by an alter.. add column... then the row will be
rebuilt prperly and wasted dpcae reclaimed.
Overflows typically cause two I/O's to get the actual row to be worked on.
and also uses twice the amount of space (1 page in bp for each row).
HTH, Pierre.

--
Pierre Saint-Jacques
SES Consultants Inc.
514-737-4515
"Anton Versteeg via DBMonster.com" <fo***@DBMonster.com> a écrit dans le
message de news: 51***********@DBMonster.com...

hi****@gmail.com wrote:

I have taken a table snapshot, and noticed two tables with high
overflows. What should be done, if any.

From the System Monitor Guide:

Description: The number of accesses (reads and writes) to overflowed rows
of
this table.

Usage: Overflowed rows indicate that data fragmentation has occurred. If
this
number is high, you may be able to improve table performance by
reorganizing
the table using the REORG utility, which cleans up this fragmentation. A
row
overflows if it is updated and no longer fits in the data page where it
was
originally written. This usually happens as a result of an update of a
VARCHAR or an ALTER TABLE statement.
--
Message posted via http://www.dbmonster.com

[hikums]

Thanks Pierre!! Clear explanation.

Pierre Saint-Jacques wrote:

The only way to get things right will be to REORG the table.
REORG will get the overflow caused by the VARCHAR length increase to be
restructured and will then get rid of the overflowed row.
If the overflows are caused by an alter.. add column... then the row willbe
rebuilt prperly and wasted dpcae reclaimed.
Overflows typically cause two I/O's to get the actual row to be worked on.
and also uses twice the amount of space (1 page in bp for each row).
HTH, Pierre.

--
Pierre Saint-Jacques
SES Consultants Inc.
514-737-4515
"Anton Versteeg via DBMonster.com" <fo***@DBMonster.com> a écrit dans le
message de news: 51***********@DBMonster.com...

hi****@gmail.com wrote:

I have taken a table snapshot, and noticed two tables with high
overflows. What should be done, if any.

From the System Monitor Guide:

Description: The number of accesses (reads and writes) to overflowed rows
of
this table.

Usage: Overflowed rows indicate that data fragmentation has occurred. If
this
number is high, you may be able to improve table performance by
reorganizing
the table using the REORG utility, which cleans up this fragmentation. A
row
overflows if it is updated and no longer fits in the data page where it
was
originally written. This usually happens as a result of an update of a
VARCHAR or an ALTER TABLE statement.
--
Message posted via http://www.dbmonster.com