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Sybase Replication server Internal

Rplication server internals
-------------------------------

Functioning of all threads
-------------------------------

1> Rep Agent
---------------
a> Scans transaction log PDB
b> Converts log records to log transfer language and send to Inbound queues
c> moves the secondary truncation point
d> verifies correct object schema

2> Stable queue manager
-----------------------
a> Used to manage process of reading/writing/deleting messages on stable device

3> stable queue transaction
---------------------------
a> Passes stable device messages to clients in commit order
* Client includes DIST and DSI threads


* SQT cache size
----------------
a> Each IBQ consumes sqt_max_cache_size
b> Each DSI also takes sqt_max_cache_size


4> distributor (DIST)
---------------------
a> Calls SQT and SQM to read the IBQ in commit order
b> Destination will be an OBQ
c> Makes calls to 3 libraries
1> Subscription resolution engine
2> Transaction delivery (packs commands)
3> Message delivery - It groups messages for different subscribers over a comman route.


5> Data server interface
------------------------
Composed of DSI scheduler thread and DSI executor threads
a> Schedular is queue manager
1> Reads transactions from outbound queue
2> Sorts them into commit order using SQL library
3> Decides the grouping,batching of transactions
b> Executor delivers to the RDS
1> Reads transactions from DSI SQT cache
2> Maps function strings
3> Handles error actions (error checks before sending commit)


6> Groupmg logic
----------------
a> Transaction may be grouped if they
1> are in memory (SQT closed)
2> are from same origin
3> have the same username and password
b> Groups are up to dsi_xact_group_size
bytes (default 64 K)
c> Sent in batches of dsi_cmd_batch_size
bytes



* Replication server users
--------------------------
1> Maintainance user
Used by replication server to make changes in replicate databases.

2> Repagent user
Used by repagents to log into replication server

3> Primary RSSD user
Used by replication server to make changes to its own RSSD

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