SystemMonitor

Monitor certain critical c-tree Server events.

Short Name

SYSMON()

Type

Server only function

Declaration

COUNT SystemMonitor(COUNT mode, LONG timeout, pTEXT buffer, VRLEN buflen)

Description

SystemMonitor() provides the ability for a client to monitor certain critical c-tree Server events. Each event causes a message to be written to an internal queue. Each call to SystemMonitor() reads a message from this queue. If no message is available, it waits for a message or times out.

mode can take on two values:

SYSMON_MAIN monitors the beginning and end of dynamic dumps and occurrence of file mirroring events.
SYSMON_OFF turns off the monitoring.

timeout specifies the time in seconds for a forced return of SystemMonitor() in the event that no event occurs. A value of -1L indicates an unlimited wait: SystemMonitor returns only when an event occurs or the Server stops. Note that the monitor is still in effect after a timeout return. For another process to start monitoring, the client currently monitoring must disconnect from the Server or call SystemMonitor() with the SYSMON_OFF mode.

buffer points to the buffer which receives a descriptive Server monitor message.

buflen is the length of the buffer.

Return

SystemMonitor() returns one of the following values. More events may be added in future releases.

Value	Symbolic Constant	Explanation
0	NO_ERROR	When Server terminates.
156	NTIM_ERR	Monitor timed-out without event.
454	NSUP_ERR	System monitor not supported (non-server).
542	MCRE_ERR	Could not create mirror file.
543	MOPN_ERR	Could not open mirror file.
544	MCLS_ERR	Could not close mirror file.
545	MDLT_ERR	Could not delete mirror file.
546	MWRT_ERR	Could not write to mirror file.
547	MSAV_ERR	Could not save mirror file.
548	MRED_ERR	Could not read (header) in mirror.
549	MHDR_ERR	Mismatch between mirror headers.
550	MSKP_ERR	Attempt to open primary w/o mirror.
551	MNOT_ERR	File already opened without mirror.
555	PREA_ERR	Could not read primary file, all I/O performed on mirror file only.
556	PWRT_ERR	Could not write primary file, all I/O performed on mirror file only.
557	CWRT_ERR	Could not write mirror file, all I/O performed on primary file only.
558	PSAV_ERR	Could not save primary file, all I/O performed on mirror file only.
559	CSAV_ERR	Could not save mirror file, all I/O performed on primary file only.
560	SMON_ERR	Only one of each monitor at a time.
561	DDMP_BEG	Dynamic dump begins.
562	DDMP_END	Dynamic dump ends.
563	DDMP_ERR	Dynamic dump ends with errors.

When coding the “switch” or other constructs to handle the SystemMonitor() return codes, be sure to provide a default to handle return codes which may be added in future implementations. See “c-tree Plus Error Codes” in the c-tree Plus Programmer’s Reference Guide for a complete listing of valid c-tree Plus error values.

Example

VRLEN     buflen=128;

TEXT      buffer[128];   /* input buffer */

LONG      timeout = 10;


while(SystemMonitor(SYSMON_MAIN,timeout,buffer,buflen)) {

    switch(uerr_cod){

        case NSUP_ERR:

            printf("No monitor support\n");

            StopUser();

            exit(0);

        case NTIM_ERR:

            break;

        case PREA_ERR:

        case PWRT_ERR:

        case PSAV_ERR:

            printf("Primary file not operational (%d)\n%s\n", uerr_cod,buffer);

            break;

        case CWRT_ERR:

        case CSAV_ERR:

            printf("Mirror file not operational (%d)\n%s\n", uerr_cod,buffer);

            break;

        default:

            printf("other monitor event(%d)\n%s\n", uerr_cod, buffer);

            break;

    }    /* end of switch */

}    /* end of while */


/* if server has terminated */

StopUser();

exit(0);

Limitations

Available only with the c-tree Server. A call to SystemMonitor() on a non-server system results in error return NSUP_ERR (454).

Only one application connected to each Server may have SystemMonitor() active.