IBM E16RMLL-I Implementation Guide - Page 533
Maxschedsessions, Tcpwindowsize
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that the server must handle. If you need 10 concurrent nodes to perform backup operations and each of them has a multi-threading capability (resource utilization) of 4, then you must set maxsession to at least 40 (10 x 4). MAXSCHEDSESSIONS The MAXSCHEDSESSIONS parameter specifies the number of sessions that the server can use for processing scheduled operations. It is specified as a percentage of the total number of server sessions available (the MAXSESSION parameter). You should set this to less than 100, otherwise it could lead to a situation where all the available sessions are being used for running client scheduled backups and a critical restore cannot run because there are no spare session slots. Use the query status command to display the current MAXSCHEDSESSIONS value, and change it to another value with the set maxschedsessions command. TCPWINDOWSIZE This option specifies the size of the TCP sliding window in kilobytes. The TCPWINDOWSIZE option overrides the operating system's TCP send and receive spaces. In AIX, for instance, these parameters are named tcp_sendspace and tcp_recvspace. The TCPWINDOWSIZE option specifies the size of the TCP sliding window for all clients and all but MVS servers. A larger window size can improve communication performance, but uses more memory. It enables multiple frames to be sent before an acknowledgment is obtained from the receiver. If long transmission delays are being observed, increasing the TCPWINDOWSIZE may improve throughput. The size of the TCP/IP buffer is used when sending or receiving data. The window size used in a session is the smaller of the server and client window sizes. Larger window sizes use additional memory but may improve performance. The general recommendation is to set TCPWINDOWSIZE to 64 (except Windows, which is 63). Clients now default to 63. In an SP2 environment with a high-speed switch set the TCPWINDOWSIZE to a value between 128-640, and when using Gigabit Ethernet with Jumbo Frames - 9000 MTU set the TCPWINDOWSIZE to 128. Tip: On AIX, the network option rfc1323 must be set on to have TCPWindow sizes larger than 64K-1. Chapter 15. Performance considerations 503