What is variable &G$UNIQID? How is it set? Can it be changed?
'&G$' variables are CA SYSVIEW-related variables, and if you enter the command VLIST you will see them along with their associated values.
They differ from the '&' variables which are System variables, e.g. &SMFID and &SYSNAME. System variables are not related to CA SYSVIEW and can be used in any JCL which you could run on any system.
&G$UNIQID defaults to 'GSVXnnn', where nnn is the release number.
For example, CA SYSVIEW r12.0 gives &G$UNIQID a value of 'GSVX120' by default.
You will find &G$UNIQID referred to in many CA SYSVIEW PARMLIB members. For example, in member CICSLOGR you will see: LOGSTREAM-CICSSYSD-NAME &G$UNIQID..CICSLOGR.SYSD.&SMFID where &G$UNIQID is the high level node.
Should you want to keep a common value for &G$UNIQID when you upgrade CA SYSVIEW then you will need to change the &G$UNIQID reference in those PARMLIB members accordingly.
This could for example enable you to continue to use your current log stream names after upgrading (if compatibility is not an issue).
The value you code in the INST0012 job parameter ANCHORN for the CA SYSVIEW Subsystem Name (usually GSVX) allows you to have a &G$UNIQID variable that resolves to something other than 'GSVX' followed by the release number.