Partner application's maximum security acceptance level

Before using such security features, the application program must know what security level its potential conversation partners can support. VTAM® determines the partner's level of support for security when the first session with a partner LU is established. VTAM returns this information to the application program in the RPL extension. This information is returned when an APPCCMD CONTROL=ALLOC or APPCCMD CONTROL=OPRCNTL, QUALIFY=DISPLAY macroinstruction completes and activates the first session between the two LUs. Three bits in the RPL extension indicate the partner LU's security acceptance level. The bit settings are shown in Table 1.

Table 1. Partner LU's security acceptance level
Security Level		RPL6X Bits
	RPL6CLSA	RPL6AVFA	RPL6PV
NONE	0	0	0
CONV	1	0	0
ALREADYV	1	1	0
PERSISTV	1	0	1
AVPV	1	1	1

To determine the partner LU's support for conversation-level security, the application program issues APPCCMD CONTROL=OPRCNTL, QUALIFY=DISPLAY and examines 3 bits in the returned session limits display (ISTSLD) structure. The bit settings for each security level are shown in Table 2.

Table 2. Partner LU's support for conversation-level security
Security Level		ISTSLD Bits
	SLDPCLSA	SLDPAVFA	SLDPPV
NONE	0	0	0
CONV	1	0	0
ALREADYV	1	1	0
PERSISTV	1	0	1
AVPV	1	1	1

Note: The application program can issue APPCCMD CONTROL=OPRCNTL, QUALIFY=DISPLAY before the first session with the partner LU is activated and before the partner LU's support for conversation-level security is determined. In this case, the bits in the session limits display structure are not valid. Therefore, when the application program issues APPCCMD CONTROL=OPRCNTL, QUALIFY=DISPLAY, it first must check a bit in the session limits display structure, SLDCSLV, to determine whether the bits that indicate the partner's security acceptance level are valid.