Hi,

I have a global temp table that I'm using in a stored procedure.. the execution time of the procedure seems to be REALLY slow and I want to experiment a little to figure out if I can make it faster.. here's what I have for the temp tablespace --

CREATE USER TEMPORARY TABLESPACE USERTMP_TBLSP IN DATABASE PARTITION GROUP IBMDEFAULTGROUP PAGESIZE 4096 MANAGED BY SYSTEM
USING ('/path1/path2')
EXTENTSIZE 32
PREFETCHSIZE 32
BUFFERPOOL IBMDEFAULTBP
OVERHEAD 12.670000
TRANSFERRATE 0.180000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY OFF;

Here are the parameters for another regular tablespace --

CREATE REGULAR TABLESPACE MAIN_TBLSP IN DATABASE PARTITION GROUP MAIN_GROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path1/path2')
EXTENTSIZE 32
PREFETCHSIZE 96
BUFFERPOOL MAIN_BP
OVERHEAD 24.100000
TRANSFERRATE 0.900000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY ON;


Is there anything I should change in the USERTMP_TBLSP parameters that would help me improve performance ? Thanks!!!

Hi,

what's the size of IBMDEFAULTBP?

You should turn off FILE SYSTEM CACHING, if the Bufferpool has a sufficient size or is set to automatic.

Different values for OVERHEAD and TRANSFERRATE for the tablespaces does not make sense, if you use the same disks. The default values are changed from Version to Version since the Performace of disks changes too.

Tuning of Extentsize and Prefetchsize requires some knowledge about the disklayout.

thanks for the reply! If I give the command db2 "select * from syscat.bufferpools", I get this ---

IBMDEFAULTBP
NPAGES = 1000
PAGESIZE = 4096

Also, am really not sure how or why the values of OVERHEAD and TRANSFERRATE were set to the current numbers.


Won't file system caching set to ON make data retrieval faster if the procedure has already been called before?


On a side note, if you're getting the monthly data sum value for an entity... basically getting the sum of values from 8929 records,how long do you think that should take.. my query takes this long --

real 0m8.696s
user 0m0.000s
sys 0m0.012s

Which Version of DB2 are you using and what OS?

The IBMDEFAULTBP is set to the default size. Currently the BP has a size of 4 MB.
According to your System, the amount of free and the Size of your UserTemp you should increase the size of the Bufferpool.

If you have activated the Filesystem Caching then you are caching in the Database (bufferpools) and in the Filesystem. This is not very useful.
Only Tablespaces for Large Objects (BLOBs, CLOBs etc) should use Filesystem Caching, because DB2 is not caching the IOs for LOBs.

Thanks, am using DB2 version 8.2 UDB on a Linux Server. Here are the partition groups, bufferpools and tablespaces that have been setup --


CREATE DATABASE PARTITION GROUP "NGROUP" ON DBPARTITIONNUMS
(0);


CREATE DATABASE PARTITION GROUP "R_GROUP" ON DBPARTITIONNUMS
(0);


CREATE DATABASE PARTITION GROUP "P_GROUP" ON DBPARTITIONNUMS
(0);


CREATE DATABASE PARTITION GROUP "REGROUP" ON DBPARTITIONNUMS
(0);


------------------------------------
-- DDL Statements for BUFFERPOOLS --
------------------------------------

CREATE BUFFERPOOL "BP" DATABASE PARTITION GROUP "NGROUP" SIZE 10000 PAGESIZE 8192 NOT EXTENDED STORAGE;

CREATE BUFFERPOOL "R_BP" DATABASE PARTITION GROUP "R_GROUP" SIZE 10000 PAGESIZE 8192 NOT EXTENDED STORAGE;

CREATE BUFFERPOOL "TEMPSP2_BP" DATABASE PARTITION GROUP "IBMTEMPGROUP" SIZE 2000 PAGESIZE 8192 NOT EXTENDED STORAGE;

CREATE BUFFERPOOL "P_BP" DATABASE PARTITION GROUP "P_GROUP" SIZE 2000 PAGESIZE 8192 NOT EXTENDED STORAGE;

CREATE BUFFERPOOL "C_BP" DATABASE PARTITION GROUP "P_GROUP" SIZE 2000 PAGESIZE 8192 NOT EXTENDED STORAGE;

CREATE BUFFERPOOL "RE_BP" DATABASE PARTITION GROUP "REGROUP" SIZE 3000 PAGESIZE 8192 NOT EXTENDED STORAGE;

------------------------------------
-- DDL Statements for TABLESPACES --
------------------------------------

CREATE REGULAR TABLESPACE MAIN_TBLSP IN DATABASE PARTITION GROUP NGROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path1/path2')
EXTENTSIZE 32
PREFETCHSIZE 96
BUFFERPOOL BP
OVERHEAD 24.100000
TRANSFERRATE 0.900000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY ON;

CREATE REGULAR TABLESPACE R_TBLSP IN DATABASE PARTITION GROUP R_GROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path/...')
EXTENTSIZE 32
PREFETCHSIZE 192
BUFFERPOOL R_BP
OVERHEAD 24.100000
TRANSFERRATE 0.900000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY ON;

CREATE TEMPORARY TABLESPACE TEMPSPACE2 IN DATABASE PARTITION GROUP IBMTEMPGROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path...')
EXTENTSIZE 32
PREFETCHSIZE 192
BUFFERPOOL TEMPSP2_BP
OVERHEAD 24.100000
TRANSFERRATE 0.900000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY OFF;

CREATE REGULAR TABLESPACE P_TBLSP IN DATABASE PARTITION GROUP P_GROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path...')
EXTENTSIZE 32
PREFETCHSIZE 192
BUFFERPOOL P_BP
OVERHEAD 24.100000
TRANSFERRATE 0.900000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY ON;


CREATE REGULAR TABLESPACE C_TBLSP IN DATABASE PARTITION GROUP P_GROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path...')
EXTENTSIZE 32
PREFETCHSIZE 192
BUFFERPOOL C_BP
OVERHEAD 24.100000
TRANSFERRATE 0.900000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY ON;

CREATE REGULAR TABLESPACE R_TBLSP IN DATABASE PARTITION GROUP REGROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path....')
EXTENTSIZE 32
PREFETCHSIZE 96
BUFFERPOOL RE_BP
OVERHEAD 12.670000
TRANSFERRATE 0.180000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY ON;

CREATE REGULAR TABLESPACE SYSTOOLSPACE IN DATABASE PARTITION GROUP IBMCATGROUP PAGESIZE 4096 MANAGED BY SYSTEM
USING ('/home/dn2inst1/db2inst1/NODE0000/SQL00001/SYSTOOLSPACE')
EXTENTSIZE 32
PREFETCHSIZE 32
BUFFERPOOL IBMDEFAULTBP
OVERHEAD 12.670000
TRANSFERRATE 0.180000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY ON;

CREATE USER TEMPORARY TABLESPACE USERTMP_TBLSP IN DATABASE PARTITION GROUP IBMDEFAULTGROUP PAGESIZE 4096 MANAGED BY SYSTEM
USING ('/path...')
EXTENTSIZE 32
PREFETCHSIZE 32
BUFFERPOOL IBMDEFAULTBP
OVERHEAD 12.670000
TRANSFERRATE 0.180000
FILE SYSTEM CACHING
DROPPED TABLE RECOVERY OFF;

So should I increase the size of IBMDEFAULTBP? or just associate USERTMP_TBLSP with a brand new partition group / bufferpool that's bigger in size?

Like this?


CREATE DATABASE PARTITION GROUP "USERGROUP" ON DBPARTITIONNUMS
(0);


CREATE BUFFERPOOL "USERTMP_BP" DATABASE PARTITION GROUP "USERGROUP" SIZE 2000 PAGESIZE 8192 NOT EXTENDED STORAGE;


CREATE USER TEMPORARY TABLESPACE USERTMP_TBLSP IN DATABASE PARTITION GROUP IBMDEFAULTGROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/path...')
EXTENTSIZE 32
PREFETCHSIZE 32
BUFFERPOOL USERTMP_BP
OVERHEAD 12.670000
TRANSFERRATE 0.180000
NO FILE SYSTEM CACHING
DROPPED TABLE RECOVERY OFF;



Thanks for the help!

Just thought I'd add that I changed it to 'NO FILE SYSTEM CACHING' and it didn't seem to help the processing time

Huh,

that's a lot of Questions ...

I don't know your System. Why do you have so many Partition Groups? Is there a reason for it?
All your Bufferpools are pretty small. The larger ones have a size of 80 MB. Smaller ones have 16 MB. IBMDEFAULTBP has 4 MB.

Could you give us some Information?

> db2pd -osinfo
> db2 get snapshot for bufferpools on <DATABASE>

thanks.. am really not sure why there were so many partition groups setup to begin with..

here is what I get from the above commands :

db2pd -osinfo

Operating System Information:

OSName: Linux
NodeName: <systemname>
Version: 2
Release: 6
Machine: x86_64

CPU Information:
TotalCPU OnlineCPU ConfigCPU Speed(MHz) HMTDegree Cores/Socket
4 4 4 2393 1 1

Physical Memory and Swap (Megabytes):
TotalMem FreeMem AvailMem TotalSwap FreeSwap
7937 25 n/a 7633 7577

Virtual Memory (Megabytes):
Total Reserved Available Free
15570 n/a n/a 7602

Message Queue Information:
MsgSeg MsgMax MsgMap MsgMni MsgTql MsgMnb MsgSsz
n/a 8192 16384 1024 16384 16384 16

Shared Memory Information:
ShmMax ShmMin ShmIds ShmSeg
1073741824 1 4096 4096

Semaphore Information:
SemMap SemMni SemMns SemMnu SemMsl SemOpm SemUme SemUsz SemVmx SemAem
32000 1024 32000 32000 250 32 n/a 20 32767 32767

CPU Load Information:
Short Medium Long
0.070000 0.050000 0.010000




db2 get snapshot for bufferpools on dbname

Bufferpool Snapshot

Bufferpool name = IBMDEFAULTBP
Database name = db2name
Database path = /path/
Input database alias = db2name
Snapshot timestamp = 10/13/2010 13:58:35.153332

Buffer pool data logical reads = Not Collected
Buffer pool data physical reads = Not Collected
Buffer pool temporary data logical reads = Not Collected
Buffer pool temporary data physical reads = Not Collected
Buffer pool data writes = Not Collected
Buffer pool index logical reads = Not Collected
Buffer pool index physical reads = Not Collected
Buffer pool temporary index logical reads = Not Collected
Buffer pool temporary index physical reads = Not Collected
Total buffer pool read time (milliseconds) = Not Collected
Total buffer pool write time (milliseconds)= Not Collected
Asynchronous pool data page reads = Not Collected
Asynchronous pool data page writes = Not Collected
Buffer pool index writes = Not Collected
Asynchronous pool index page reads = Not Collected
Asynchronous pool index page writes = Not Collected
Total elapsed asynchronous read time = Not Collected
Total elapsed asynchronous write time = Not Collected
Asynchronous data read requests = Not Collected
Asynchronous index read requests = Not Collected
No victim buffers available = Not Collected
Direct reads = Not Collected
Direct writes = Not Collected
Direct read requests = Not Collected
Direct write requests = Not Collected
Direct reads elapsed time (ms) = Not Collected
Direct write elapsed time (ms) = Not Collected
Database files closed = Not Collected
Data pages copied to extended storage = Not Collected
Index pages copied to extended storage = Not Collected
Data pages copied from extended storage = Not Collected
Index pages copied from extended storage = Not Collected
Unread prefetch pages = Not Collected
Vectored IOs = Not Collected
Pages from vectored IOs = Not Collected
Block IOs = Not Collected
Pages from block IOs = Not Collected
Physical page maps = Not Collected

Node number = 0
Tablespaces using bufferpool = 5
Alter bufferpool information:
Pages left to remove = 0
Current size = 1000
Post-alter size = 1000

Bufferpool Snapshot

Bufferpool name = BP
Database name = dbname
Database path = /path
Input database alias = dbname
Snapshot timestamp = 10/13/2010 13:58:35.153332

Buffer pool data logical reads = Not Collected
Buffer pool data physical reads = Not Collected
Buffer pool temporary data logical reads = Not Collected
Buffer pool temporary data physical reads = Not Collected
Buffer pool data writes = Not Collected
Buffer pool index logical reads = Not Collected
Buffer pool index physical reads = Not Collected
Buffer pool temporary index logical reads = Not Collected
Buffer pool temporary index physical reads = Not Collected
Total buffer pool read time (milliseconds) = Not Collected
Total buffer pool write time (milliseconds)= Not Collected
Asynchronous pool data page reads = Not Collected
Asynchronous pool data page writes = Not Collected
Buffer pool index writes = Not Collected
Asynchronous pool index page reads = Not Collected
Asynchronous pool index page writes = Not Collected
Total elapsed asynchronous read time = Not Collected
Total elapsed asynchronous write time = Not Collected
Asynchronous data read requests = Not Collected
Asynchronous index read requests = Not Collected
No victim buffers available = Not Collected
Direct reads = Not Collected
Direct writes = Not Collected
Direct read requests = Not Collected
Direct write requests = Not Collected
Direct reads elapsed time (ms) = Not Collected
Direct write elapsed time (ms) = Not Collected
Database files closed = Not Collected
Data pages copied to extended storage = Not Collected
Index pages copied to extended storage = Not Collected
Data pages copied from extended storage = Not Collected
Index pages copied from extended storage = Not Collected
Unread prefetch pages = Not Collected
Vectored IOs = Not Collected
Pages from vectored IOs = Not Collected
Block IOs = Not Collected
Pages from block IOs = Not Collected
Physical page maps = Not Collected

Node number = 0
Tablespaces using bufferpool = 1
Alter bufferpool information:
Pages left to remove = 0
Current size = 10000
Post-alter size = 10000


Bufferpool Snapshot

Bufferpool name = R_BP
Database name = dbname
Database path = /path
Input database alias = dbname
Snapshot timestamp = 10/13/2010 13:58:35.153332

Buffer pool data logical reads = Not Collected
Buffer pool data physical reads = Not Collected
Buffer pool temporary data logical reads = Not Collected
Buffer pool temporary data physical reads = Not Collected
Buffer pool data writes = Not Collected
Buffer pool index logical reads = Not Collected
Buffer pool index physical reads = Not Collected
Buffer pool temporary index logical reads = Not Collected
Buffer pool temporary index physical reads = Not Collected
Total buffer pool read time (milliseconds) = Not Collected
Total buffer pool write time (milliseconds)= Not Collected
Asynchronous pool data page reads = Not Collected
Asynchronous pool data page writes = Not Collected
Buffer pool index writes = Not Collected
Asynchronous pool index page reads = Not Collected
Asynchronous pool index page writes = Not Collected
Total elapsed asynchronous read time = Not Collected
Total elapsed asynchronous write time = Not Collected
Asynchronous data read requests = Not Collected
Asynchronous index read requests = Not Collected
No victim buffers available = Not Collected
Direct reads = Not Collected
Direct writes = Not Collected
Direct read requests = Not Collected
Direct write requests = Not Collected
Direct reads elapsed time (ms) = Not Collected
Direct write elapsed time (ms) = Not Collected
Database files closed = Not Collected
Data pages copied to extended storage = Not Collected
Index pages copied to extended storage = Not Collected
Data pages copied from extended storage = Not Collected
Index pages copied from extended storage = Not Collected
Unread prefetch pages = Not Collected
Vectored IOs = Not Collected
Pages from vectored IOs = Not Collected
Block IOs = Not Collected
Pages from block IOs = Not Collected
Physical page maps = Not Collected

Node number = 0
Tablespaces using bufferpool = 1
Alter bufferpool information:
Pages left to remove = 0
Current size = 10000
Post-alter size = 10000


Bufferpool Snapshot

Bufferpool name = TEMPSP2_BP
Database name = dbname
Database path = /path
Input database alias = dbname
Snapshot timestamp = 10/13/2010 13:58:35.153332

Buffer pool data logical reads = Not Collected
Buffer pool data physical reads = Not Collected
Buffer pool temporary data logical reads = Not Collected
Buffer pool temporary data physical reads = Not Collected
Buffer pool data writes = Not Collected
Buffer pool index logical reads = Not Collected
Buffer pool index physical reads = Not Collected
Buffer pool temporary index logical reads = Not Collected
Buffer pool temporary index physical reads = Not Collected
Total buffer pool read time (milliseconds) = Not Collected
Total buffer pool write time (milliseconds)= Not Collected
Asynchronous pool data page reads = Not Collected
Asynchronous pool data page writes = Not Collected
Buffer pool index writes = Not Collected
Asynchronous pool index page reads = Not Collected
Asynchronous pool index page writes = Not Collected
Total elapsed asynchronous read time = Not Collected
Total elapsed asynchronous write time = Not Collected
Asynchronous data read requests = Not Collected
Asynchronous index read requests = Not Collected
No victim buffers available = Not Collected
Direct reads = Not Collected
Direct writes = Not Collected
Direct read requests = Not Collected
Direct write requests = Not Collected
Direct reads elapsed time (ms) = Not Collected
Direct write elapsed time (ms) = Not Collected
Database files closed = Not Collected
Data pages copied to extended storage = Not Collected
Index pages copied to extended storage = Not Collected
Data pages copied from extended storage = Not Collected
Index pages copied from extended storage = Not Collected
Unread prefetch pages = Not Collected
Vectored IOs = Not Collected
Pages from vectored IOs = Not Collected
Block IOs = Not Collected
Pages from block IOs = Not Collected
Physical page maps = Not Collected

Node number = 0
Tablespaces using bufferpool = 1
Alter bufferpool information:
Pages left to remove = 0
Current size = 2000
Post-alter size = 2000

Bufferpool Snapshot

Bufferpool name = P_BP
Database name = dbname
Database path = /path
Input database alias = dbname
Snapshot timestamp = 10/13/2010 13:58:35.153332

Buffer pool data logical reads = Not Collected
Buffer pool data physical reads = Not Collected
Buffer pool temporary data logical reads = Not Collected
Buffer pool temporary data physical reads = Not Collected
Buffer pool data writes = Not Collected
Buffer pool index logical reads = Not Collected
Buffer pool index physical reads = Not Collected
Buffer pool temporary index logical reads = Not Collected
Buffer pool temporary index physical reads = Not Collected
Total buffer pool read time (milliseconds) = Not Collected
Total buffer pool write time (milliseconds)= Not Collected
Asynchronous pool data page reads = Not Collected
Asynchronous pool data page writes = Not Collected
Buffer pool index writes = Not Collected
Asynchronous pool index page reads = Not Collected
Asynchronous pool index page writes = Not Collected
Total elapsed asynchronous read time = Not Collected
Total elapsed asynchronous write time = Not Collected
Asynchronous data read requests = Not Collected
Asynchronous index read requests = Not Collected
No victim buffers available = Not Collected
Direct reads = Not Collected
Direct writes = Not Collected
Direct read requests = Not Collected
Direct write requests = Not Collected
Direct reads elapsed time (ms) = Not Collected
Direct write elapsed time (ms) = Not Collected
Database files closed = Not Collected
Data pages copied to extended storage = Not Collected
Index pages copied to extended storage = Not Collected
Data pages copied from extended storage = Not Collected
Index pages copied from extended storage = Not Collected
Unread prefetch pages = Not Collected
Vectored IOs = Not Collected
Pages from vectored IOs = Not Collected
Block IOs = Not Collected
Pages from block IOs = Not Collected
Physical page maps = Not Collected

Node number = 0
Tablespaces using bufferpool = 1
Alter bufferpool information:
Pages left to remove = 0
Current size = 2000
Post-alter size = 2000


Bufferpool Snapshot

Bufferpool name = C_BP
Database name = dbname
Database path = /path
Input database alias = dbname
Snapshot timestamp = 10/13/2010 13:58:35.153332

Buffer pool data logical reads = Not Collected
Buffer pool data physical reads = Not Collected
Buffer pool temporary data logical reads = Not Collected
Buffer pool temporary data physical reads = Not Collected
Buffer pool data writes = Not Collected
Buffer pool index logical reads = Not Collected
Buffer pool index physical reads = Not Collected
Buffer pool temporary index logical reads = Not Collected
Buffer pool temporary index physical reads = Not Collected
Total buffer pool read time (milliseconds) = Not Collected
Total buffer pool write time (milliseconds)= Not Collected
Asynchronous pool data page reads = Not Collected
Asynchronous pool data page writes = Not Collected
Buffer pool index writes = Not Collected
Asynchronous pool index page reads = Not Collected
Asynchronous pool index page writes = Not Collected
Total elapsed asynchronous read time = Not Collected
Total elapsed asynchronous write time = Not Collected
Asynchronous data read requests = Not Collected
Asynchronous index read requests = Not Collected
No victim buffers available = Not Collected
Direct reads = Not Collected
Direct writes = Not Collected
Direct read requests = Not Collected
Direct write requests = Not Collected
Direct reads elapsed time (ms) = Not Collected
Direct write elapsed time (ms) = Not Collected
Database files closed = Not Collected
Data pages copied to extended storage = Not Collected
Index pages copied to extended storage = Not Collected
Data pages copied from extended storage = Not Collected
Index pages copied from extended storage = Not Collected
Unread prefetch pages = Not Collected
Vectored IOs = Not Collected
Pages from vectored IOs = Not Collected
Block IOs = Not Collected
Pages from block IOs = Not Collected
Physical page maps = Not Collected

Node number = 0
Tablespaces using bufferpool = 1
Alter bufferpool information:
Pages left to remove = 0
Current size = 2000
Post-alter size = 2000


Bufferpool Snapshot

Bufferpool name = RE_BP
Database name = dbname
Database path = /path
Input database alias = dbname
Snapshot timestamp = 10/13/2010 13:58:35.153332

Buffer pool data logical reads = Not Collected
Buffer pool data physical reads = Not Collected
Buffer pool temporary data logical reads = Not Collected
Buffer pool temporary data physical reads = Not Collected
Buffer pool data writes = Not Collected
Buffer pool index logical reads = Not Collected
Buffer pool index physical reads = Not Collected
Buffer pool temporary index logical reads = Not Collected
Buffer pool temporary index physical reads = Not Collected
Total buffer pool read time (milliseconds) = Not Collected
Total buffer pool write time (milliseconds)= Not Collected
Asynchronous pool data page reads = Not Collected
Asynchronous pool data page writes = Not Collected
Buffer pool index writes = Not Collected
Asynchronous pool index page reads = Not Collected
Asynchronous pool index page writes = Not Collected
Total elapsed asynchronous read time = Not Collected
Total elapsed asynchronous write time = Not Collected
Asynchronous data read requests = Not Collected
Asynchronous index read requests = Not Collected
No victim buffers available = Not Collected
Direct reads = Not Collected
Direct writes = Not Collected
Direct read requests = Not Collected
Direct write requests = Not Collected
Direct reads elapsed time (ms) = Not Collected
Direct write elapsed time (ms) = Not Collected
Database files closed = Not Collected
Data pages copied to extended storage = Not Collected
Index pages copied to extended storage = Not Collected
Data pages copied from extended storage = Not Collected
Index pages copied from extended storage = Not Collected
Unread prefetch pages = Not Collected
Vectored IOs = Not Collected
Pages from vectored IOs = Not Collected
Block IOs = Not Collected
Pages from block IOs = Not Collected
Physical page maps = Not Collected

Node number = 0
Tablespaces using bufferpool = 1
Alter bufferpool information:
Pages left to remove = 0
Current size = 3000
Post-alter size = 3000

Hi,

lots and lots of "Not Collected". You need to turn on the Monitor Switch for Bufferpools.
For your Session:
update monitor switches using bufferpool on global

Permanently:
update dbm cfg using DFT_MON_BUFPOOL on

Turn on the switches and let the System run for a period of time, e.g. when you run the procedure.