This chapter contains the environmental limits, field length maxima, and syntax definitions for all RTR C programming API calls.

3.1 RTR Environmental Limits

RTR deals with several environmental entities that have architectural limits as shown in Table 3-1. Actual limits in a specific configuration are determined by performance.

Table 3-1 Environmental Limits

Component	Limit
BE or TR nodes	512
Bytes per message	64000
Channels per application process	1024
Facilities	100 to 1000, depending on operating system
FE nodes	1000
Journal files	16
Memory per process	OpenVMS: 4GB; UNIX: unlimited; NT: 2GB
Messages per transaction - server to client	unlimited
Messages per transaction - client to server	65534
Partitions	65536 (dynamic; default:500)
Processes per node	1000
Size of journal file	256MB
Threads per application process (where supported by operating system)	4096

3.2 RTR Maximum Field Lengths

Table 3-2 contains definitions of RTR field length maxima. The file rtr.h contains values for these field lengths.

Table 3-2 RTR Maximum Field-Length Definitions

Field Name	Description
RTR_MAX_ACCESS_LEN	Maximum length of access string.
RTR_MAX_BLOB_LEN	Maximum length of data that can be passed in a prepare call.
RTR_MAX_FACNAM_LEN	Maximum length of facility name.
RTR_MAX_FE_NAM_LEN	Maximum length of frontend name.
RTR_MAX_MSGFMT_LEN	Maximum length of message format.
RTR_MAX_MSGLEN	Maximum length of an RTR message.
RTR_MAX_NUMSEG	Maximum number of segments in key.
RTR_MAX_PARNAM_LEN	Maximum length of partition name.
RTR_MAX_RCPNAM_LEN	Maximum length of broadcast recipient name.
RTR_MAX_RCPSPC_LEN	Maximum length for broadcast recipient specification.
RTR_MAX_SELVAL_LEN	Maximum length for selector value.

3.3 RTR C API Calls

The calls are presented in alphabetical order.

Accept the transaction currently active on the specified channel.

Syntax

status = rtr_accept_tx (channel, flags, reason)

Argument	Data Type	Access
status	rtr_status_t	write
channel	rtr_channel_t	read
flags	rtr_acc_flag_t	read
reason	rtr_reason_t	read

C Binding

rtr_status_t rtr_accept_tx (

rtr_channel_t channel ,
rtr_acc_flag_t flags ,
rtr_reason_t reason
)

Arguments

channel

The channel identifier (returned earlier by rtr_open_channel() ).

flags

Flags that specify options for the call.

Table 3-3 shows the flags that are defined.

Table 3-3 Accept Transaction Flags

Flag name	Description
RTR_F_ACC_FORGET	Set to prevent receipt of any more messages (or completion status) associated with the transaction. Any such messages are discarded. This flag is valid only on server channels; it has no effect on client channels.
RTR_F_ACC_INDEPENDENT	Set to indicate this transaction is independent. (See Section 2.15.4 for further information.)

If you do not require any flags, specify RTR_NO_FLAGS for this parameter.

reason

Optional reason for accepting the transaction. This reason is ORed together with the reasons of the other participants in the transaction and returned in the reason field of the rtr_status_data_t structure returned with the rtr_mt_accepted message to all participants of the transaction. Specify RTR_NO_REASON if no reason is required.

Description

The rtr_accept_tx() call accepts the transaction currently active on the specified channel. After rtr_accept_tx() has been called, the caller may no longer actively participate in the fate of the transaction; that is, messages and the final completion status can still be received, but no further messages may be sent for the transaction. An attempt to send a further message yields an RTR_STS_TXALRACC return status.

Example

/* * Client is done with the txn; if the server accepts the * transaction, there is no reason for us to reject it. * Accept it, then go on to a new transaction. */ if (msgsb.msgtype == rtr_mt_accepted) { status = rtr_accept_tx( channel, RTR_NO_FLAGS, RTR_NO_REASON ); check_status( status ); } else . . Issue the error message returned by the . server, and recover from there. .

See Also

rtr_open_channel()
rtr_reject_tx()
rtr_reply_to_client()

Broadcast (send) a user event message.

Syntax

status = rtr_broadcast_event (channel, flags, pmsg, msglen, evtnum, rcpspc, msgfmt)

Argument	Data Type	Access
status	rtr_status_t	write
channel	rtr_channel_t	read
flags	rtr_bro_flag_t	read
pmsg	rtr_msgbuf_t	read
msglen	rtr_msglen_t	read
evtnum	rtr_evtnum_t	read
rcpspc	rtr_rcpspc_t	read
msgfmt	rtr_msgfmt_t	read

C Binding

rtr_status_t rtr_broadcast_event (

rtr_channel_t channel ,
rtr_bro_flag_t flags ,
rtr_msgbuf_t pmsg ,
rtr_msglen_t msglen ,
rtr_evtnum_t evtnum ,
rtr_rcpspc_t rcpspc ,
rtr_msgfmt_t msgfmt
)

Arguments

channel

The channel identifier (returned earlier by rtr_open_channel() ).

flags

No flags are currently defined. Specify RTR_NO_FLAGS for this parameter.

pmsg

Pointer to the message to broadcast.

msglen

Length in bytes of the message broadcast.

evtnum

User event number associated with this broadcast. (Recipients must specify this to receive it.) For more information on user event numbers, see Section 2.12.

rcpspc

Name of the recipient(s). This null-terminated character string contains the name of the recipient(s), specified with the rcpnam parameter on the call to rtr_open_channel() .

Wildcards ( "*" for any sequence of characters, and "%" for any one character) can be used in this string to address more than one recipient. rcpspc is an optional parameter. Specify RTR_NO_RCPSPC for this parameter if no rcpspc is required.

Note To receive named events, the correct event number must also be specified. The event number (evtnum) must be specified by both the sender (rcpspc) and the recipient (rcpnam). Both rcpnam and rcpspc are case sensitive. Both rcpnam and rcpspc default to the case-insensitive channel name if no explicit rcpnam or rcpspc is provided.

msgfmt

Message format description. This null-terminated character string contains the format description of the message. RTR uses this description to convert the contents of the message appropriately when processing the message on different hardware platforms. See Section 2.14 for information on defining a message format description.

This parameter is optional. Specify RTR_NO_MSGFMT if message content is platform independent, or there is no intent to use other hardware platforms.

Description

The rtr_broadcast_event() call broadcasts a user event message. The caller must first open a channel (using rtr_open_channel() ), before it can send user event messages.

A client channel can be used to send user event messages to servers.

A server channel can be used to send user event messages to clients.

Example

#define reunion_announcement 678 // In user .h file. rtr_msg_buf_t reunion_msg = "Jones family reunion today!"; rtr_rcpspc_t recipients = "*Jones"; /* * If today is the date of the Jones family reunion, tell * any client whose last name is Jones that they need to * be there! */ if (strcmp(today, reunion_date) == 0) { status = rtr_broadcast_event( &channel, RTR_NO_FLAGS, reunion_msg, strlen(reunion_msg), reunion_announcement, recipients, RTR_NO_MSGFMT ); check_status( status ); }

See Also

rtr_receive_message()
rtr_open_channel()

Close a previously opened channel.

Syntax

status = rtr_close_channel (channel, flags)

Argument	Data Type	Access
status	rtr_status_t	write
channel	rtr_channel_t	read
flags	rtr_clo_flag_t	read

C Binding

rtr_status_t rtr_close_channel (

rtr_channel_t channel ,
rtr_clo_flag_t flags
)

Arguments

channel

The channel identifier (returned earlier by rtr_open_channel() , or rtr_request_info() or rtr_set_info() ).

flags

Flags that specify options for the call.

The flag RTR_F_CLO_IMMEDIATE is defined for this call.

Normally rtr_close_channel() processes a pending transaction that was in a commit state by forgetting the transaction (removing it from the journal). To close the channel but leave transactions in the journal, use the flag RTR_F_CLO_IMMEDIATE to rtr_close_channel() .

In some situations, an accepted transaction cannot be completed and replay is required. For example, a transaction may be accepted but the database becomes unavailable before the transaction is committed to the database. To deal with such a situation, an application can use the close-immediate flag RTR_F_CLO_IMMEDIATE. This closes the channel but leaves the transactions in the journal for use on replay when database access is restored. If you do not need any flags, specify RTR_NO_FLAGS for this argument.

Description

The rtr_close_channel() call closes a previously opened channel. A channel may be closed at any time after it has been opened via rtr_open_channel() or rtr_request_info() . If the channel is a server channel, an implicit acknowledgment is sent, if you have a current transaction.

Example

/* If the status returned by the previous call is not success, * close now, and exit the program. */ if (status != RTR_STS_OK) { printf(fpLog, "Unexpected error, must close immediately!"); status = rtr_close_channel( channel, RTR_CLO_IMMEDIATE); exit(status); } /* * Normal processing complete, close the channel. */ printf(fpLog, "Closing channel"); status = rtr_close_channel ( channel, RTR_NO_FLAGS );

See Also

rtr_open_channel()

Return the text associated with an RTR status value.

Syntax

retval = rtr_error_text (sts)

Argument	Data Type	Access
retval	char*	write
sts	rtr_status_t	read

C Binding

char *rtr_error_text (

rtr_status_t sts
)

Arguments

sts

The RTR error number for which the text is required.

Description

The rtr_error_text() call returns a pointer to the text associated with an RTR error number.

The text string is a constant. If an invalid value for sts is supplied, a pointer is also returned to an error text, indicating an invalid value.

Example

/* If the status returned by the previous call is not success, * print the message text to the error log, and exit. */ if (status != RTR_STS_OK) { printf(errLog, rtr_error_text(status)); exit(status); }

Broadcast (send) a user event message or an RTR_STS_TIMOUT status if RTR is unable to issue to broadcast message within the specified timeout period. The call is the same as rtr_broadcast_event with the addition of the timeout period, given in milliseconds.

Syntax

status = rtr_ext_broadcast_event (channel, flags, pmsg, msglen, evtnum, rcpspc, msgfmt, timoutms)

Argument	Data Type	Access
status	rtr_status_t	write
channel	rtr_channel_t	read
flags	rtr_bro_flag_t	read
pmsg	rtr_msgbuf_t	read
msglen	rtr_msglen_t	read
evtnum	rtr_evtnum_t	read
rcpspc	rtr_rcpspc_t	read
msgfmt	rtr_msgfmt_t	read
timoutms	rtr_timout_t	read

C Binding

rtr_status_t rtr_ext_broadcast_event (

rtr_channel_t channel ,
rtr_bro_flag_t flags ,
rtr_msgbuf_t pmsg ,
rtr_msglen_t msglen ,
rtr_evtnum_t evtnum ,
rtr_rcpspc_t rcpspc ,
rtr_msgfmt_t msgfmt ,
rtr_timout_t timoutms
)

Arguments

channel

The channel identifier (returned earlier by rtr_open_channel() ).

flags

No flags are currently defined. Specify RTR_NO_FLAGS for this parameter.

pmsg

Pointer to the message to broadcast.

msglen

Length in bytes of the message to be broadcast.

evtnum

User event number associated with this broadcast. (Recipients must specify this to receive it.) For more information on user event numbers, see Section 2.12.

rcpspc

Name of the recipient(s). This null-terminated character string contains the name of the recipient(s), specified with the rcpnam parameter on the call to rtr_open_channel() .

Wildcards ( "*" for any sequence of characters, and "%" for any one character) can be used in this string to address more than one recipient. rcpspc is an optional parameter. Specify RTR_NO_RCPSPC for this parameter if no rcpspc is required.

Note To receive named events, the correct event number must also be specified. The event number (evtnum) must be specified by both the sender (rcpspc) and the recipient (rcpnam). Both rcpnam and rcpspc are case sensitive. Both rcpnam and rcpspc default to the case-insensitive channel name if no explicit rcpnam or rcpspc is provided.

msgfmt

Message format description. This null-terminated character string contains the format description of the message. RTR uses this description to convert the contents of the message appropriately when processing the message on different hardware platforms. See Section 2.14 for information on defining a message format description.

This parameter is optional. Specify RTR_NO_MSGFMT if message content is platform independent, or there is no intent to use other hardware platforms.

timoutms

Timeout value in milliseconds that the call will wait before tiing out. Returns status RTR_STS_TIMOUT if RTR is unable to process the call. If no timeout is needed, specify RTR_NO_TIMOUTMS.

Description

The rtr_ext_broadcast_event() call broadcasts a user event message. The caller must first open a channel (using rtr_open_channel() ), before it can send user event messages.

A client channel can be used to send user event messages to servers.

A server channel can be used to send user event messages to clients.

In some circumstances, a broadcast event can wait a long time if RTR runs out of channel credits; it may seem that the application is hanging. To eliminate such a wait, the application can specify a timeout value from which the call returns an RTR_STS_TIMOUT status if RTR is unable to issue the broadcast message within the specified timeout period.