I've just made an experience, that impdp over network is sometimes slow and sometimes fast:
I have a "source" database (lets say A), with version 184.108.40.206, and two "destination" databases B (220.127.116.11) and C (18.104.22.168).
The data size is about 100 GB. Import from A into B needes about 4.5 hours, and import from A into C takes about 1.5 hours.
The data which is moved are identical. I've also checked the wait states, and we have found out, that database B makes a lot of log switches
during import, which is the reason, why database B is such slow. On database C there are almost no log switches.
B has log switches frequency about one in 2 seconds. C has aprox. 6 log switches in the first 30 minutes (during DATA load).
That database B has logswitches, and C not let me think about Direct Load versus External Table Load, which is described in the documentation.
But this seems different when using network_link: the trace of the DW process does not support this information (but should, as described in 552424.1).
I think, there are some bugs/features fixed/changed between 22.214.171.124 and 126.96.36.199 regarding load strategy over network_link.
There might be also a chance, that a initial parameter is different between B and C causing to different behavior, but
Does anyone have a similar observation? Does anyone know about this "change"?
The users have all the same grants, the data are exact equal (by FLASHBACK_TIME), remap_schema and remap_tablespace are used at both.
there is a bug in 188.8.131.52 where indexes are not created in parallel - which would be fixed in 184.108.40.206. Might explain the overall time difference as indexes are often the longest part of the load?
Database A is in archive mode, B and C not.
The problem is in the data transfer, not at index generation.
For C, the data transfer is 30 min, Index generation is about 1h.
For B, the data transfer is about 200 min, Index generation in about 1h.
I have one new information: We have switched back after this to dumpfile transfer, and interesting: With dumpfile, the import is done with Direct Path.