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Top Forums Programming DB2 - Performance Issue using MERGE option Post 303018332 by rbatte1 on Monday 4th of June 2018 07:03:36 AM
Old 06-04-2018
I expect that this is doing what you asked, and although it does seem a sensible query, it is not being very practical. I think that your request is going to build some huge temporary tables to work out the various clauses before applying any inserts/updates. You may even fill your temporary table tablespace before your MERGE completes this step.


You might have some success with indices though. What indices do you have on table schemaname.Customer_Staging and schemaname.Customer_Staging?
  • If you don't have a single index for the three columns you mention in the SELECT DISTINCT, then you might do a full table scan of schemaname.Customer_Staging.
  • If you don't have a single index for all the columns in the whole query (e.g A.Name, B.Name, A.Load_dt etc. ) then you might do a full table scan of the appropriate table.
Any reason to do a full table scan that these scales will be bad. An index might take a while to build and needs to have space, but then your MERGE should run better. I've had something that took me 20 minutes to build an index then the process I wanted ran in about an hour, after which I dropped the index again.because it was a one-off report. The run without the index was abandoned after over 22 hours (someone set if off and went home)

Is there some sort of query profiler you can use to consider this? MSSQLServer has one, Oracle has one so I'm sure that DB2 will have one, but I've not ever used it. You need to avoid a full table scan when dealing with this volume of data.



I hope that this helps,
Robin

Last edited by rbatte1; 06-04-2018 at 08:03 AM.. Reason: Spelling correction.
 

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DB2_GET_OPTION(3)							 1							 DB2_GET_OPTION(3)

db2_get_option - Retrieves an option value for a statement resource or a connection resource

SYNOPSIS
string db2_get_option (resource $resource, string $option) DESCRIPTION
Retrieves the value of a specified option value for a statement resource or a connection resource. PARAMETERS
o $resource - A valid statement resource as returned from db2_prepare(3) or a valid connection resource as returned from db2_connect(3) or db2_pconnect(3). o $option - A valid statement or connection options. The following new options are available as of ibm_db2 version 1.6.0. They provide use- ful tracking information that can be set during execution with db2_get_option(3). Note Prior versions of ibm_db2 do not support these new options. When the value in each option is being set, some servers might not handle the entire length provided and might truncate the value. To ensure that the data specified in each option is converted correctly when transmitted to a host system, use only the characters A through Z, 0 through 9, and the underscore (_) or period (.). o $userid - SQL_ATTR_INFO_USERID - A pointer to a null-terminated character string used to identify the client user ID sent to the host database server when using DB2 Connect. Note DB2 for z/OS and OS/390 servers support up to a length of 16 characters. This user-id is not to be confused with the authentication user-id, it is for identification purposes only and is not used for any authorization. o $acctstr - SQL_ATTR_INFO_ACCTSTR - A pointer to a null-terminated character string used to identify the client accounting string sent to the host database server when using DB2 Connect. Note DB2 for z/OS and OS/390 servers support up to a length of 200 characters. o $applname - SQL_ATTR_INFO_APPLNAME - A pointer to a null-terminated character string used to identify the client application name sent to the host database server when using DB2 Connect. Note DB2 for z/OS and OS/390 servers support up to a length of 32 characters. o $wrkstnname - SQL_ATTR_INFO_WRKSTNNAME - A pointer to a null-terminated character string used to identify the client workstation name sent to the host database server when using DB2 Connect. Note DB2 for z/OS and OS/390 servers support up to a length of 18 characters. The following table specifies which options are compatible with the available resource types: Resource-Parameter Matrix +-----------+--------------------------+---+---+---+ | Key | | | | | | | | | | | | | Value | | | | | | | | | | | | Resource Type | | | | | | | | | | +-----------+--------------------------+---+---+---+ |Connection | | | | | | | | | | | | | Statement | | | | | | | | | | | | Result Set | | | | | | | | | | | userid | | | | | | | | | | | | | | | | | | | SQL_ATTR_INFO_USERID | | | | | | | | | | | | X | | | | | | | | | | | | X | | | | | | | | | | | | - | | | | | | | | | | | acctstr | | | | | | | | | | | | | | | | | | | SQL_ATTR_INFO_ACCTSTR | | | | | | | | | | | | X | | | | | | | | | | | | X | | | | | | | | | | | | - | | | | | | | | | | | applname | | | | | | | | | | | | | | | | | | | SQL_ATTR_INFO_APPLNAME | | | | | | | | | | | | X | | | | | | | | | | | | X | | | | | | | | | | | | - | | | | | | | | | | |wrkstnname | | | | | | | | | | | | | | | | | | | SQL_ATTR_INFO_WRKSTNNAME | | | | | | | | | | | | X | | | | | | | | | | | | X | | | | | | | | | | | | - | | | | | | | | | | +-----------+--------------------------+---+---+---+ RETURN VALUES
Returns the current setting of the connection attribute provided on success or FALSE on failure. EXAMPLES
Example #1 Setting and retrieving parameters through a connection resource <?php /* Database Connection Parameters */ $database = 'SAMPLE'; $user = 'db2inst1'; $password = 'ibmdb2'; /* Obtain Connection Resource */ $conn = db2_connect($database, $user, $password); echo "Client attributes passed through connection string: "; /* Create the associative options array with valid key-value pairs */ /* Assign the attributes through connection string */ /* Access the options specified */ $options1 = array('userid' => 'db2inst1'); $conn1 = db2_connect($database, $user, $password, $options1); $val = db2_get_option($conn1, 'userid'); echo $val . " "; $options2 = array('acctstr' => 'account'); $conn2 = db2_connect($database, $user, $password, $options2); $val = db2_get_option($conn2, 'acctstr'); echo $val . " "; $options3 = array('applname' => 'myapp'); $conn3 = db2_connect($database, $user, $password, $options3); $val = db2_get_option($conn3, 'applname'); echo $val . " "; $options4 = array('wrkstnname' => 'workstation'); $conn4 = db2_connect($database, $user, $password, $options4); $val = db2_get_option($conn4, 'wrkstnname'); echo $val . " "; echo "Client attributes passed post-connection: "; /* Create the associative options array with valid key-value pairs */ /* Assign the attributes after a connection is made */ /* Access the options specified */ $options5 = array('userid' => 'db2inst1'); $conn5 = db2_connect($database, $user, $password); $rc = db2_set_option($conn5, $options5, 1); $val = db2_get_option($conn5, 'userid'); echo $val . " "; $options6 = array('acctstr' => 'account'); $conn6 = db2_connect($database, $user, $password); $rc = db2_set_option($conn6, $options6, 1); $val = db2_get_option($conn6, 'acctstr'); echo $val . " "; $options7 = array('applname' => 'myapp'); $conn7 = db2_connect($database, $user, $password); $rc = db2_set_option($conn7, $options7, 1); $val = db2_get_option($conn7, 'applname'); echo $val . " "; $options8 = array('wrkstnname' => 'workstation'); $conn8 = db2_connect($database, $user, $password); $rc = db2_set_option($conn8, $options8, 1); $val = db2_get_option($conn8, 'wrkstnname'); echo $val . " "; ?> The above example will output: Client attributes passed through connection string: db2inst1 account myapp workstation Client attributes passed post-connection: db2inst1 account myapp workstation SEE ALSO
db2_connect(3), db2_cursor_type(3), db2_exec(3), db2_set_option(3), db2_pconnect(3), db2_prepare(3). PHP Documentation Group DB2_GET_OPTION(3)
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