You indicate on the PROTOCOL attribute of the SESSIONS resource definition whether the sessions allocated on the MRO connection are for use by the external CICS® interface. See the CICS Resource Definition Guide for full details of the SESSIONS resource definition. The following parameters are relevant to EXCI:
For MRO, receive sessions can only receive before sending.
If you are using the default receive prefix (<), or your own 1-character prefix, specify a number in the range 1 through 999.
If you specify a 2-character prefix, the number is restricted to the range 1 through 99.
Except for external CICS interface (EXCI) connections, the RECEIVECOUNT in this system should equal SENDCOUNT in the other system.
Prefixes must not cause a conflict with an existing connection or terminal name.
CICS creates the last three characters of the session names from the alphanumeric characters A through Z, and 1 through 9. These 3-character identifiers begin with the letters AAA, and continue in ascending sequence until the number of session entries reaches the limit set by the RECEIVECOUNT value. Note that receive session names are generated after the send sessions, and they follow in the same sequence.
For example, if the last session name generated for the send sessions is <AAJ, using the default prefix (<) CICS generates the receive session names as <AAK, <AAL, <AAM, and so on. (This method of generation of session identifiers is the same as for APPC sessions, except for the initial prefix symbol.)
For LUTYPE6.1 sessions (and MRO if you specify your own 1- or 2-character prefix) CICS generates session names by appending a number to the prefix, either in the range 1 through 99, or 1 through 999. The number begins with 1 and is incremented by 1 until the specified RECEIVECOUNT is reached.
For MRO, send sessions must send before they can receive.
You must leave this field blank when the sessions are on an external CICS interface (EXCI) connection.
If you are using the default send prefix (>), or your own 1-character prefix, specify a number in the range 1 through 999.
If you specify a 2-character prefix, the number is restricted to the range 1 through 99.
Except for external CICS interface (EXCI) connections the SENDCOUNT in the sending system should equal RECEIVECOUNT in the receiving system.
Prefixes must not cause a conflict with an existing connection or terminal name.
CICS creates the last three characters of the session names from the alphanumeric characters A through Z, and 1 through 9. These 3-character identifiers begin with the letters AAA, and continue in ascending sequence until the number of session entries reaches the limit set by the SENDCOUNT value.
For example, using the default prefix (>) CICS generates session names as >AAA, >AAB, >AAC, and so on. (This method of generation of session identifiers is the same as for APPC sessions, except for the initial symbol.)
For LUTYPE6.1 sessions (and MRO if you specify your own 1- or 2-character prefix) CICS generates session names by appending a number to the prefix, either in the range 1 through 99, or 1 through 999. The number begins with 1 and is incremented by 1 until the specified SENDCOUNT is reached.
If you do not specify a preset userid for link security, CICS uses the userid passed from the remote user as the userid for link security, which in the case of an external CICS interface link is the client userid.