Oracle Data Pump Export expdp Tuning Tips

Question:  I am using the Data Pump Utility for an export with expdp, and it runs terribly slow.  What are techniques for speeding-up an export?  Are there performance tuning techniques for exports?

Answer:  Yes, there are several techniques for speeding up Oracle exports.  I recommend Bert Scalzo's book "Oracle Utilities" for a full discussion of export performance tuning, and these tips for using the export query clause.

• Use a parallel export - You can [parallelize your export to degree cpu_count-1, but it is important to remember to also split to dmp file so that expdp can write to multiple files at the same time.  The %u argument allows Oracle to create multiple dump files, one for each parallel process:

expdp dumpfile=filename.%u.dmp parallel=31

• Traditional export vs., Data Pump Export - Some benchmark tests indicate that the traditional export utility (exp) runs twice as fast as the Data Pump export (expdp).
  
  
• Use a Larger Export Buffer - For conventional path exports, a larger buffer will increase the number of rows that are processed between each physical write to the export file. Fewer physical writes equals greater performance. The following formula can be used to determine a proper buffer size:
  
  buffer size = rows in array * max row size
  
• Separate the Tables - Separate those tables that require consistent=y from those that don't, in order to expedite the export. This way, the performance penalty will only be incurred for those tables that actually require it.
  
  
• Use Direct Path - Direct path exports (direct=y) allow the export utility to skip the SQL evaluation buffer, whereas the conventional path export executes SQL SELECT statements. With direct path, the data is read from disk into the buffer cache, returning rows directly to the export client. This can offer substantial performance gains, depending on the actual data. When using the direct path, the recordlength parameter should also be used to optimize performance.
  
  
• Use faster media - An expert is I/O intensive and exporting from faster media like SSD will greatly reduce total export time.
  
  
• Use export Subsets - By sub-setting the data using the export query option, the export process is only executed against the data that needs to be exported. If tables have old rows that are never updated, the old data should be exported once, and from that point only the newer data subsets should be exported. Subsets cannot be specified with direct path exports since SQL is necessary to create the subset.

expdp / file=$file tables=myexport query\=" where myexport_pidm in (select myexport_pidm from purdue.myexport where myexport_to_extract\=\'Y\' and myexport_export_status\=\'N\')\"