Synchronous mode copy waits for the completion of remote write operation when explicit or  implicit synchronous CCW is issued by mainframe or TS7700 internal buffer becomes full. For  a single application perspective, the elapsed time might become longer than other copy  modes when network latency is relatively long. For example, the required time for  DFSMShsm secondary space management might be affected in the longer network latency.  Draft Document for Review February 7, 2020 4:43 pm 8464ch12_Performance.fm 12.7.4 Tuning possibilities for copies: COPYCOUNT Control  Tuning the counts of the number of concurrent copy jobs over the grid links can be done for  several reasons, Values can be set for the number of concurrent RUN copy threads and the number of  Deferred copy threads. The allowed values for the copy thread count are 5 - 128. The default  value is 20 for clusters with two 1-Gbps Ethernet links, and 40 for clusters with four 1-Gbps or  two 10-Gbps Ethernet links. Use the following parameters with the  LIBRARY  command: GLYPH<SM590000> SETTING, COPYCNT, RUN GLYPH<SM590000> SETTING, COPYCNT, DEF Increasing the copy count can be beneficial if the following conditions exist: Increase the copy count  GLYPH<SM590000> The gridlinks are not saturated. GLYPH<SM590000> The number of small logical volumes is high.  GLYPH<SM590000> An upgrade from 2 to 4 grid links was made, and the number of copy tasks were not  adjusted. In this case, an increase of the copy count might reduce the RPO.  Be aware that often one gridlink with 1 Gbps can be saturated by 10 copies running in  parallel. If the logical volumes are small, you might see gaps in the grid link usage, when only  a few copies are running, because some volumes finished, and new lvols where selected for  copy processing. In this situation, it might be beneficial to have more copies running  concurrently.  Consider that if too many copies are running concurrently, the grid link is overflowed. This  issue can result in package loss and retries, and lead overall to a lower performance of the  grid link environment. If you want to increase the number, do so in smaller steps (5 or 10) to become familiar with  the new setting. In addition, do not define values that are too high, especially if you use  synchronous mode copy concurrently to the RUN and Deferred traffic.  Chapter 12. Performance considerations  725 Synchronous mode copy considerations Copies can be halted by a  disable gridlink  command. No Yes Subject Synchronous mode copy Run or Deferred mode