Solution : https://service.sap.com/sap/support/notes/68896 (SAP Service marketplace login required)
Summary : 
      This SAP Note addresses performance issues with client operations in R3trans, specifically copying, exporting, deleting, and importing, which sometimes exceed usual runtimes. Detailed benchmarks for throughput such as 120 MB/hour for client copying and 80 MB/hour for client deletion are provided. Key performance bottlenecks identified include inefficient handling of cluster and transparent tables, main memory limitations, and database-specific problems like inadequate indexing or lock issues. Solutions offered range from pre-deletion of large clusters to optimize operations to direct manipulation of physical cluster tables to avoid unnecessary logical processing and improve speed significantly in releases before 3.1G.
Key words : 
administration -> system administration -> monitor -> performance -> database -> tables/indexes, bsec bsed bseg bses bsetthe end, import  file = '/usr/sap/trans/data/cluster, file = '/usr/sap/trans/data/cluster, file /usr/sap/trans/data/cluster, directory /usr/sap/trans/tmp, development -> dictionary -> environment -> information system, objects -> select pooled/cluster tables, cdhdr cdpos pcdhdr pcdpos, remaining client specific table entries
Related Notes : 
       
| 1223360 | Composite SAP Note: Performance optimization during import | 
| 339721 | CC INFO: Subsequent copy of long texts | 
| 333534 | R3trans: Performance during import of table with INT fields | 
| 311147 | R3trans refuses import of a physical cluster | 
| 138639 | Poor DML performance with Oracle DDIC statistics | 
| 102034 | R3trans: Control of the COMMIT intervals | 
| 65946 | Lock escalations | 
| 65594 | CC-INFO: Client copy for cluster table is slow | 
| 60233 | Oracle rollback segments, more information. | 
| 34150 | Missing table entries in table T185 | 
| 28293 | Trans, SapDba, WP's under NT > 3.5 is hanging | 
| 15374 | Checklist: Performance analysis | 
| 12621 | SAPDBA: speeding up a reorganization | 
| 6588 | R3trans: Memory allocation failed |