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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_CLIENT_INFO(3)							 1							DB2_CLIENT_INFO(3)

db2_client_info - Returns an object with properties that describe the DB2 database client

SYNOPSIS
object db2_client_info (resource $connection) DESCRIPTION
This function returns an object with read-only properties that return information about the DB2 database client. The following table lists the DB2 client properties: DB2 client properties +---------------------+--------------------------------------+---+ | Property name | | | | | | | | | Return type | | | | | | | | Description | | | | | | +---------------------+--------------------------------------+---+ | APPL_CODEPAGE | | | | | | | | | int | | | | | | | | The application code page. | | | | | | | CONN_CODEPAGE | | | | | | | | | int | | | | | | | | The code page for the current con- | | | | nection. | | | | | | | DATA_SOURCE_NAME | | | | | | | | | string | | | | | | | | The data source name (DSN) used to | | | | create the current connection to the | | | | database. | | | | | | | DRIVER_NAME | | | | | | | | | string | | | | | | | | The name of the library that imple- | | | | ments the DB2 Call Level Interface | | | | (CLI) specification. | | | | | | | DRIVER_ODBC_VER | | | | | | | | | string | | | | | | | | The version of ODBC that the DB2 | | | | client supports. This returns a | | | | string "MM.mm" where $MM is the | | | | major version and $mm is the minor | | | | version. The DB2 client always | | | | returns "03.51". | | | | | | | DRIVER_VER | | | | | | | | | string | | | | | | | | The version of the client, in the | | | | form of a string "MM.mm.uuuu" where | | | | $MM is the major version, $mm is the | | | | minor version, and $uuuu is the | | | | update. For example, "08.02.0001" | | | | represents major version 8, minor | | | | version 2, update 1. | | | | | | |ODBC_SQL_CONFORMANCE | | | | | | | | | string | | | | | | | | The level of ODBC SQL grammar sup- | | | | ported by the client: | | | | | | | | o MINIMUM | | | | - Supports the mini- | | | | mum ODBC SQL gram- | | | | mar. | | | | | | | | o CORE | | | | - Supports the core | | | | ODBC SQL grammar. | | | | | | | | o EXTENDED | | | | - Supports extended | | | | ODBC SQL grammar. | | | | | | | ODBC_VER | | | | | | | | | string | | | | | | | | The version of ODBC that the ODBC | | | | driver manager supports. This | | | | returns a string "MM.mm.rrrr" where | | | | $MM is the major version, $mm is the | | | | minor version, and $rrrr is the | | | | release. The DB2 client always | | | | returns "03.01.0000". | | | | | | +---------------------+--------------------------------------+---+ PARAMETERS
o $connection - Specifies an active DB2 client connection. RETURN VALUES
Returns an object on a successful call. Returns FALSE on failure. EXAMPLES
Example #1 A db2_client_info(3) example To retrieve information about the client, you must pass a valid database connection resource to db2_client_info(3). <?php $conn = db2_connect( 'SAMPLE', 'db2inst1', 'ibmdb2' ); $client = db2_client_info( $conn ); if ($client) { echo "DRIVER_NAME: "; var_dump( $client->DRIVER_NAME ); echo "DRIVER_VER: "; var_dump( $client->DRIVER_VER ); echo "DATA_SOURCE_NAME: "; var_dump( $client->DATA_SOURCE_NAME ); echo "DRIVER_ODBC_VER: "; var_dump( $client->DRIVER_ODBC_VER ); echo "ODBC_VER: "; var_dump( $client->ODBC_VER ); echo "ODBC_SQL_CONFORMANCE: "; var_dump( $client->ODBC_SQL_CONFORMANCE ); echo "APPL_CODEPAGE: "; var_dump( $client->APPL_CODEPAGE ); echo "CONN_CODEPAGE: "; var_dump( $client->CONN_CODEPAGE ); } else { echo "Error retrieving client information. Perhaps your database connection was invalid."; } db2_close($conn); ?> The above example will output: DRIVER_NAME: string(8) "libdb2.a" DRIVER_VER: string(10) "08.02.0001" DATA_SOURCE_NAME: string(6) "SAMPLE" DRIVER_ODBC_VER: string(5) "03.51" ODBC_VER: string(10) "03.01.0000" ODBC_SQL_CONFORMANCE: string(8) "EXTENDED" APPL_CODEPAGE: int(819) CONN_CODEPAGE: int(819) SEE ALSO
db2_server_info(3). PHP Documentation Group DB2_CLIENT_INFO(3)
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