Options for which you must choose values

For some options in your APPL statement, you must supply a specific value; for others, Db2 suggests values that are not the VTAM® default values.

In your APPL statement, you must code values for the following options:

name

The 1 to 8 character LU name you chose. For their USIBMSTODB21 Db2 system, Spiffy uses LUDB21.

AUTOSES

The number of contention winner sessions that VTAM is to activate automatically between this Db2 and another system on a given mode before Db2 requests a conversation to be created.

Contention occurs when two LUs want to allocate a conversation at the same time in the same session. In order to resolve contention situations, VTAM denotes one LU as the contention winner and one as the contention loser. The winner automatically prevails and is allowed to allocate its conversation. The loser must wait to allocate its conversation.

The default is 0. The suggested value is 1 or greater to ensure that VTAM informs Db2 if a session is inactivated.

Too large a number can take up storage and create resources that are not used. A small number can result in a one-time delay to bring up additional sessions when they are needed by an application.

DMINWNL

The minimum number of parallel sessions in which, if there is contention for a conversation, this local Db2 subsystem is the winner.

The suggested value is one-half the value of DSESLIM, described below.

DMINWNR

For the same situation as described for DMINWNL, the number of sessions in which the remote system is the winner. The suggested value is one-half the value of DSESLIM, described below.

DSESLIM

The default maximum number of sessions allowed for this Db2 subsystem as it communicates with any other system on a given mode. For performance reasons, the Db2 suggested value for DSESLIM is the maximum number of sessions that can possibly be in use on any mode. For example, assume you have 5 modes for which the following maximum numbers of sessions could be active: 10, 12, 20, 30, 40. In this case, DSESLIM should be 40.

Because calculating a precise value for this number can be rather difficult if you do not know exactly how many applications run on a specific mode, Spiffy chooses 50. They can modify this option later if they have problems obtaining enough sessions, or if they find they are requesting sessions that they never need.

You can use DSESLIM to control the number of sessions that this subsystem can issue or receive. For example, to avoid overloading this subsystem with requests from remote application processes, you can assign a low number to DSESLIM to limit the number of simultaneous remote requests issued by a given partner and mode.

Use the CONVLIMIT column of the LUMODES table in the CDB to override this value for specific cases.

MODETAB

The name of the VTAM logon mode table you use to define Db2 session modes. Only modes defined in this table are eligible for conversations created by the local Db2. If you leave this blank, Db2 uses the default mode table shipped with VTAM (ISTINCLM). Spiffy decides to set up a separate mode table and chooses the name DB2MODES. Db2 cannot use either the default mode table or the one you set up yourself until you make entries into the table.

PRTCT

If you decided to use a password, this is that password. Later, you must store the same password in the bootstrap data set (BSDS), entering it through installation panels or the change log inventory utility.

If you prefer not to use a password, omit this option. The installation panels and the change log inventory utility do not require you to enter a password.

SECACPT

The level of conversation-level security allowed.

Recommendation: Use ALREADYV, which gives you the most flexibility in determining your security. You can use the CDB to determine levels of security on a more granular basis.

In general, SECACPT=CONV should not be used because in many cases, it does not allow already verified conversations for DRDA access.

VERIFY

Whether you want SNA partner LU verification. The default, VERIFY=NONE, means that any system can connect with yours. Because Spiffy is setting up a small, restricted network, it chooses the default for now.

Use VERIFY=REQUIRED to activate partner LU verification. This means that you let RACF® and VTAM check the identity of an LU that is attempting to connect with yours.

Db2 has no dependency on the value you choose.

VPACING

The maximum number of messages that another system can send to this local Db2 subsystem during a conversation before waiting to receive a pacing response. The suggested value is 2.

These message sizes are determined by the RUSIZES option of the MODEENT macro. VPACING and RUSIZES, together with some overhead, determine the amount of storage required for the pacing window.