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When the replication mode details auxiliary system is not available, the primary system is synchronized.

The synchronous primary system waits for the secondary system to receive the data and persist it to disk. If the master system waits to operate logshipping_timeout (default is 30 seconds)

The primary system will continue to run without replicating data.

Memory synchronization

The synchronous-in memory primary system waits for the secondary system to receive data. If the master system waits to operate logshipping_timeout (default is 30 seconds)

The primary system will continue to run without replicating data.

Full synchronization

Synchronous full sync

(SPS 08 and higher) the primary system waits for the secondary system to receive the data and persist it to disk. The primary system is blocked until the standby system is available.

The Asynchronous primary system does not have to wait for the secondary system. The primary system continues to run without replicating data.

The operating mode SAP HANA version describes the advantages of delta_datashipping unlimited synchronization between the primary site and the secondary site through regular periods from the primary site to the secondary site

Incremental data transfer. * the memory footprint of the secondary site can be smaller because the column storage table does not have to be loaded during system replication

* therefore, you can set up global_allocation_limit (SAP doc 1999997) and run another non-production system on the same machine.

* History tables are generally supported (for logreplay schemas, the limitations described in SAP doc 2480889 apply)

Logreplay > = 1.00.110 synchronization between the primary and secondary sites is based entirely on the redo log. * Delta data transfer is no longer required

* reduce network traffic between primary and secondary sites

* reduce network bandwidth requirements between primary and secondary sites

* reduced takeover time (shorter log replay, no persistent garbage collection, no file ID mapping and disk LOB initialization, no resource container configuration adjustments; see SAP doc 2222217)

* logical persistence corruption is not propagated at the disk level (for example, introduced by bug described in SAP doc 2375691). Logreplay_readaccess > = 2.00 synchronization between primary and secondary sites is based entirely on redo logs

Secondary sites can be used for read-only access (storing tables in columns). * the same advantages as the "logreplay" above

* query load can be removed from the main site.

In a 3-tier environment, the logreplay pattern can consider the following details:

* if the third system goes down, the log is saved only on the secondary system, not on the primary system.

* if the secondary system goes down and you want to use the third system as the secondary system, you usually need full synchronization because the logs retained on the primary site are for the secondary site, so they may not be compatible with the third system.

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