Hi Peter,
If a default is not specified for a CI-SIZE in ISMF, then you will see a blank, however, the default is always 4K as you observed with LISTCAT.
The default CI-SIZE of 4K is documented in a few different places in IBM documentation, but it is also in the help for the "CISIZE DATA" column in ISMF as well.
CI-SIZE can not be specified via log stream definition. It must be specified via an SMS data class definition whose CI-SIZE is set to the desired size.
LS_SIZE is the size of an offload data set. For most log streams, there are a maximum of 168 of these.
STG_SIZE is the size of the in-memory (and on-disk in many cases) staging area logger uses to buffer data before it offloads the data to an aforementioned offload data set.
CI-SIZE, which has much less to do with the log stream and more to do with how the operating system asks for data from disk, is basically the amount of data the OS will ask disk for at a time. In other words, we are recommending that the CI-SIZE be changed from 4K to 24K to reduced the number of times the system logger needs to go to disk and ask for data. This is important to improve the rate of read from the log stream. This has no affect on how much data the log stream can store. It only affects how the log stream moves data around, in this case more efficiently.
Jason Brosius
CA SYSVIEW