Some Facts about DATA PUMP Parallel=n option
- By default the value of the parallel option is 1
- Export job creates those many threads specified in the parallel option.
- The value of the parallel option can be modified in interactive mode.
- This option used with %U clause in the filename parameter of the expdp/impdp
- Resource consumption can be controlled using the parallel option. PARALLEL is the only tuning parameter that is specific to the Data Pump
- It is recommended that the value of the parameter should not be more than 2 times of number of CPUs in the database server for the optimum performance
- Example : expdp trans/trans SCHEMAS=trans DIRECTORY=exportdir DUMPFILE=exptrans%U.dmp PARALLEL=3
Syntax to import above dump file: imppdp trans/trans DIRECTORY=exportdir DUMPFILE=exptrans%U.dmp PARALLEL=3
- In transportable tablespace export, the degree of parallelism cannot be greater than 1.
- If a substitution variable (%U) were specified along with the PARALLEL parameter, then one file for each template is initially created. More files are created from the templates as they are needed based on how much data is being exported and how many parallel processes are given work to perform during the job.
- During import (impdp) the PARALLEL parameter value should not be larger than the number of files in the dumpset