Performance problem in data replication program written in java

Question

Dear all,
I need your valuable ideas on improving below logic on replicating data fromDB2 to Oracle 9i.We have a huge tables in DB2 to replicate to Oracle side.For one table this taking lot of time.The whole app' is written in java.The current logic is Setting soft delete to specific set of records in oracel table and Reading all records from DB2 table to set only these records in oracle table to 'N' so that deleted records got soft deleted in oralce side.The DB2 query is having 3 table join and taking nearly 1minute.We are updating the oracle table in batch of 100000.For 610275 record update in batch mode it is taking 2.25 hours which has to be reduced to <1hour.The first update to all Y and second update using DB2 query is taking 2.85 hrs.
Do you have any clever idea to reduce this time?? kindly help us.we are in critical situation now.Even new approach in logic to replicate also welcome..

Answer 1

hi,
just remove joins and use for all entries.
if sy-subrc = 0.
use delete adjacent duplicates from itab comparing key fields.(it will increase performance)
then write another select statement.
endif.
some tips:
Always check the driver internal tables is not empty, while using FOR ALL ENTRIES
Avoid for all entries in JOINS
Try to avoid joins and use FOR ALL ENTRIES.
Try to restrict the joins to 1 level only ie only for tables
Avoid using Select *.
Avoid having multiple Selects from the same table in the same object.
Try to minimize the number of variables to save memory.
The sequence of fields in 'where clause' must be as per primary/secondary index ( if any)
Avoid creation of index as far as possible
Avoid operators like <>, > , < & like % in where clause conditions
Avoid select/select single statements in loops.
Try to use 'binary search' in READ internal table. Ensure table is sorted before using BINARY SEARCH.
Avoid using aggregate functions (SUM, MAX etc) in selects ( GROUP BY , HAVING,)
Avoid using ORDER BY in selects
Avoid Nested Selects
Avoid Nested Loops of Internal Tables
Try to use FIELD SYMBOLS.
Try to avoid into Corresponding Fields of
Avoid using Select Distinct, Use DELETE ADJACENT
Go through the following Document
Check the following Links
Re: performance tuning
Re: Performance tuning of program
http://www.sapgenie.com/abap/performance.htm
http://www.thespot4sap.com/Articles/SAPABAPPerformanceTunin