Using the increased CTRACE and VIT capacity

This function is automatically enabled; you are not required to perform configuration tasks to enable the new function. Your system will behave differently than it did previously; for example, you will receive informational messages and automation might yield unexpected results. You can perform the tasks in Table 1 to reduce or eliminate any unwanted changes in system behavior, to increase the size of your VIT table, or to specify a larger buffer size for the CTRACE component SYSTCPIP.

See z/OS Migration for complete migration details.

Table 1. Increased CTRACE and VIT capacity
Task Reference
Prevent start option informational messages from being issued by updating your VTAM® start option list (ATCSTRxx). Prevent the automated MODIFY TRACE command from failing by updating your automation.
  • If the SIZE parameter is specified, convert the value to megabytes.
  • If the DSPSIZE parameter is specified, delete the DSPSIZE specification.
 Adjust to the relocation of the VTAM internal trace table in z/OS Migration
Prevent other automation failures by ensuring that the automation does not expect any of the newly retired messages. Adjust to the relocation of the VTAM internal trace table in z/OS Migration
Increase the size of your VIT table by performing the following steps:
  1. Determine the new size of your VIT in megabytes.
    Restriction: If you specify a SIZE value that is larger than the default value, z/OS® will perform paging on portions of the VIT table. Before you specify a large SIZE value, ensure that you have sufficient real or auxiliary storage to contain the entire VIT. Failure to ensure sufficient storage might result in an auxiliary storage shortage. If an SVC dump is taken that includes common storage, the size of the dump data set also increases. You must also take the increase in the size of the dump data set into consideration.
  2. In order for the new size value to be applied every time VTAM is started, you must specify the new value on the SIZE operand of the TRACE start option in your VTAM start option list (ATCSTRxx).
  3. You can temporarily apply the new size value to last as long as VTAM is active. To do this, specify the new value on the SIZE parameter of the MODIFY TRACE command.
  4. Ensure the new size value is in effect by issuing the DISPLAY NET,TRACES command. Check the size as reported at the end of message IST315I.
Specify a larger buffer size for the CTRACE component SYSTCPIP. Code the TRACE CT command and specify a value up to 1024 megabytes (1024M) for the SYS1.PARMLIB member CTIEZBxx or use the command TRACE CT,nnnM,COMP=SYSTCPIP,SUB=(procedure_jobname). Modifying options with the TRACE CT command in z/OS Communications Server: IP Diagnosis Guide
Parent topic: Increased CTRACE and VIT capacity