DB2 Server for VSE & VM: Operation

SHOW BUFFERS

Displays information about the buffer pool size and usage.

Syntax

>>-SHOW BUFFERS------------------------------------------------><

Description

This command shows you whether a specific local buffer or directory buffer contains a page that comes from a data space. If a buffer contains a data space page, the FLAGS column will contain a hex value where the X'10' bit (00010000) is turned on.

To determine whether a particular page is from a data space, either check if the most significant digit of the flag is an odd number, or perform a logical AND between the FLAGS byte and X'10'. If the digit is odd, or if the result of the calculation is X'10', the page is from a data space.

For example, a FLAGS byte of X'D0':

   In Hex:   'D0' & '10' = '10'     or
 
In Binary:   11010000 & 00010000 = 00010000

Also the first digit of 'D0' ('D' or 13) is an odd number. This page is from a data space.

The FLAGS byte contains four flag bits in total:

'80'

Modified Page. The buffer page has been modified.

'40'

In Transit The buffer page is being copied to or from DASD or a data space.

'20'

New Page The buffer page is not from DASD or a data space; the buffer contains a new page.

'10'

Data Space Page The buffer page is from a data space.

The FLAGS byte does not use the four low order bits. They will always be zero.

Example

Note that the hex values under the FLAGS column are cumulative. For example, the directory buffer at address 0047A000 contains a modified (identified by X'80') data space page (identified by X'10').

+--------------------------------------------------------------------------------+
|                                                                                |
|show buffers                                                                    |
|Only used buffers are displayed.                                                |
| DBSPACE   REC       ADDR      FLAGS  FIX CNT                                   |
| Page Buffers                                                                   |
|   1      0006FC   0045C000    10      0                                        |
|   32001  000093   0045D000    00      1                                        |
|   1      000080   0045E000    10      0                                        |
|   1      00009D   0045F000    10      0                                        |
|
·
·
·
                                                                             |
|   1      00009C   00478000    10      0                                        |
|   1      00009B   00479000    10      0                                        |
| Directory Buffers                                                              |
|   1      000001   0047A000    90      0                                        |
|   1      000002   0047A200    00      0                                        |
|   1      00000D   0047A400    00      0                                        |
|
·
·
·
                                                                             |
|   6      000005   0047C800    00      0                                        |
|   31     000001   0047CA00    00      0                                        |
|ARI0065I Operator command processing is complete.                               |
+--------------------------------------------------------------------------------+