Could anybody please help me?I am looking for solution with Attunity Replicate which allow target Oracle database to ingest really big amount of transactions.
Oracle Golden Gate states that only one possible way to do it is to split incoming transactions flow in separate streams of transactions and apply them in parallel.
Please look to this short (~2 minutes) explanation from the Oracle, what is the parallel apply (Integrated Replicate):

For Oracle as a target it is an issue to apply a huge flow of transactions on one thread. The only one possible way to speed up Oracle ingestion pf transactions is to shoot SQL statements in parallel.

In Golden Gate there are two options available:
1) Split at the Extraction or datapump stage transactions flow to separate chunks of transactions by using @range function of Golden gate

2) Use new feature from the Oracle GG 12 Integrated Replicat:

Integrated Replicat enables heavy workloads to be partitioned automatically among parallel apply processes that apply multiple transactions concurrently, while preserving the integrity and atomicity of the source transaction. Both a minimum and maximum number of apply processes can be configured with the PARALLELISM and MAX_PARALLELISM parameters. Replicat automatically adds additional servers when the workload increases, and then adjusts downward again when the workload lightens.