AWR Top 5 Timed Event - SQL*Net more data to client

SQL*Net more data to client -The server process is sending more data/messages to the client

The SQL*Net more data to client Oracle metric indicates the server process is sending more data/messages to the client. The previous operation to the client was also a send.

The first session data unit (SDU) buffer of return data is written to TCP socket buffer under “SQL*Net message to client” wait event. If Oracle needs to write more data for a call than fits into the “first” SDU buffer, then further writes for that call are done under SQL*Net more data to client event.

One can check with the Network Team on the overall network performance between Application Server and Database Server and also try to increase the SDU parameter at Listener and Tnsnames Levels. In our case after increasing the SDU parameter we have seen significant reduction in the wait event.


 
SID_LIST_LISTENER =

  (SID_LIST =

    (SID_DESC =

      (SDU=32640)

      (SID_NAME = ORAKHOJ)

      (ORACLE_HOME = /export/home/oracle10)

    ))

Tnsnames.ora

ORAKHOJ = (DESCRIPTION =

    (SDU=32640)

    (ADDRESS = (PROTOCOL = TCP)(HOST = ORAKHOJServer)(PORT = 1521))

    (CONNECT_DATA =

      (SERVER = DEDICATED) (SERVICE_NAME = ORAKHOJ)

    ) )


Network bottlenecks are very common in distributed systems and those with high network traffic. They are manifested as SQL*Net wait events, below are more wait events discussed below.

SQL*Net more data from client

Def: The server is waiting on the client to send more data to its client shadow process, in an already initiated operation

Solution: Usually OK, reduce data transferred, possible Network problems.

SQL*Net more data to client

Def: The server process is sending more data/messages to the client. The previous operation to the client was also a send.

Wait Time: The actual time it took for the send to complete

Solution: Usually OK, reduce amount of data transferred, possible Network tuning needed ( SDU)

SQL*Net break/reset to client

Def: The server sends a break or reset message to the client. The session running on the server waits for a reply from the client.

Wait Time: The actual time it takes for the break or reset message to return from the client


Solution: Check for errors in sql statement

SQL*Net more data from dblink

Def :The foreground process is expecting more data from a data base link.

Wait Time: The total time it takes to read the data from the database link (including the waiting time for the data to arrive)

Solution: Reduce data transfer, check net response

SQL*Net break/reset to dblink

Def: The server sends a break or reset message to the client. The session running on the server waits for a reply from the client.

Wait Time: The actual time it takes for the break or reset message to return from the client

Solution: Check for errors in sql statement sent