TXACCBUF in the command exit points to a field containing a two-byte RDW, two bytes of indeterminate data, followed by command data.
The two-byte RDW gives a theoretical buffer maximum of 64K more or less.
Is there an actual maximal command buffer limit that is defined/enforced by CA Top Secret?
In the case of a TSSINSTX command buffer, the 2 byte length defines the length of the actual command data that follows.
There is no implied additional free data area in the buffer. In fact the area right after the command data is used for other command instance related data that must not be interfered with.
The maximum length of any TSS command has an internal limit of 4096 but we have never seen any commands approach that size.