Node Entries Table

The Node Entries table contains information about the remote ZCOM systems that communicate with the local ZCOM subsystem. Each Local-Node and Remote-Node definition in the TTGEN configuration file occupy one entry in the table. Each entry structure is 392 bytes long and has the format shown in Table 3-4 “Node Entries Table”.

NODE_NUM - Node number

This field contains a unique node number that identifies the entry.

TIMEOUT - Default timeout value for this node

This field contains timeout in seconds for requests sent to this remote node. Most remote ZCOM requests (e.g. ZOPEN, ZTIMR, etc) require a definite response from the remote ZCOM subsystem. If the response is not received within the timeout period specified by this field, error ZENTOUT (-23) is returned to the application program. This field is initialized by TTGEN with the timeout value specified in a Remote-Node definition. This field is zero for a local node entry.

FLAGS - Node status and internal flags

This bit-field structure contains bits to maintain state and other internal information about this node. The contents of this field are as follows:

STATS - Statistics for this node

This field is a data structure that contains some statistics on the data traffic for this node. The layout of this structure is shown in Table 3-5 “STATS Data Structure”.

NDSHZRVRS - Pointer to a list of receivers for node status events.

This field contains a pointer to a linked list of applications to be notified whenever this node changes state. Whenever this node changes state from up-to-down or down-to-up, a node status system event message will be sent to each program in this linked list. That is, those applications that have issued a zevent_rcvr() call to receive node status events. This field will be set to zero if there are no applications to be notified.

NHOST - The number of defined hosts in the host array.

This field contains the number of host link records defined in the HOST table below. This field is zero for a local node entry.

HOST - Host link information structure (array)

This array of structures contains information about each of the host links for this node. It can hold information on up to four host links. Each element of the array contains the fields for one host link as shown in Table 3-6 “Host Link Information Structure”.

LINKNAME - The name of the remote system

This field contains the host name or the IP address to be used in accessing the remote node via TCP/IP. If a host name is specified, it must be defined in the /etc/hosts file.

STATS - Statistics for this host link

This field is a data structure that contains some statistics on the data traffic for this link. The layout of this structure is identical to that shown above. The data in this structure is maintained by the ZNODE daemon.

FLAGS - Host link status and flags

This bit-field data structure contains information on the status of a link. It is identical to the flags structure documented above. However only the status and valid bits are currently used. The status bit indicates whether this link is currently up or not. If the link is down (status = 0), the ZNODE daemon will route remote requests on any secondary links that are up. The data in this structure is maintained by the ZNODE daemon.