>>-+-/CHECKPOINT-+--+-DUMPQ--+----------------------------------> '-/CHE--------' +-FREEZE-+ '-PURGE--' >--+-----------+--+--------+--+---------+--+---------+--+-----------+->< '-LEAVEPLEX-' '-ABDUMP-' '-QUIESCE-' '-LEAVEGR-' '-NOCQSSHUT-'
Attention: This command shuts down your IMS system. Be sure you understand the consequences of shutting down the system before you issue this command.
>>-+-/CHECKPOINT-+--+-------+---------------------------------->< '-/CHE--------' '-SNAPQ-'
>>-+-/CHECKPOINT-+--STATISTICS--------------------------------->< '-/CHE--------'
Table 24 lists the environments (DB/DC, DBCTL, and DCCTL) from which the command and keywords can be issued.
Command / Keyword | DB/DC | DBCTL | DCCTL |
---|---|---|---|
/CHECKPOINT | X | X | X |
ABDUMP | X | X | X |
DUMPQ | X | X | |
FREEZE | X | X | X |
LEAVEPLEX | X | X | X |
NOCQSSHUT | X | X | |
PURGE | X | X | X |
QUIESCE | X | X | |
SNAPQ | X | X | |
STATISTICS | X | X | X |
The /CHECKPOINT command records control and status information on the system log. /CHECKPOINT can be used to take a simple checkpoint of IMS, with the option of also dumping the contents of the message queue data sets to the system log or to shut down IMS normally. When IMS is shut down by the /CHECKPOINT command, it can be restarted with the /NRESTART command.
There are two conditions under which IMS cannot complete a shutdown normally. The most frequent is when there are multiple-page messages on a master terminal BTAM line, paging is not complete, and the master terminal is sharing a communication line with other physical terminals. It might be necessary to use the /ASSIGN command to reassign the master terminal to a line by itself so that the /IDLE command can be issued to terminate the multiple page output. If the master terminal cannot be reassigned to another line, assign it to the system console line.
The second condition occurs when a number of IMS-generated system messages are awaiting delivery to the master terminal. All system messages destined for the master terminal will be delivered, because they can impact the way the system is restarted. The master terminal operator should acknowledge delivery of a message by causing an I/O interrupt; that is, pressing PA2, which in turn causes another message to be sent, if one exists. Another option is to assign the master terminal to the system console.
When the /CHECKPOINT command is used to shut down IMS, the /BROADCAST command can be helpful in notifying the remote terminal operators that IMS is shutting down.
In a DBCTL environment, when /CHECKPOINT FREEZE ABDUMP is entered, all of the DBCTL address spaces are dumped.
Restriction: A shutdown checkpoint is not allowed in a shared-queues environment if the CQS is not available.
Connections to external subsystems (not CCTL subsystems) will be quiesced. Connection attempts originating from dependent regions will be prohibited. After all dependent region connections have terminated, the control region will terminate its connection.
The DUMPQ and SNAPQ keywords designate starting points from which the message queue data sets can be rebuilt. However, the SNAPQ option dumps the message queues online while IMS is running without causing a shutdown of IMS.
The PURGE keyword attempts to empty all the queues so that no outstanding work remains. For DBCTL, IMS performs FREEZE processing because there are no message queues.
The FREEZE keyword shuts down IMS pending actions shown in Table 25 For DBCTL, active CCTL threads are allowed to complete before this keyword takes effect. This is also true when ABDUMP is used with this keyword. In the DBCTL environment, a /CHECKPOINT command with the PURGE keyword will be processed as though the FREEZE keyword was used instead of PURGE. /CHECKPOINT FREEZE in the DBCTL environment is correct because there are no message queues to empty.
In a DBCTL environment, when /CHECKPOINT FREEZE ABDUMP is entered, all of the DBCTL address spaces are dumped.
In a shared-queues environment, the DUMPQ and PURGE keywords cause IMS to shut down (as if you entered a /CHECKPOINT FREEZE command), but the message queues are not dumped or purged because the local IMS subsystem has no local queues. To dump the shared message queues when CQS terminates, use the /CQSET command before issuing the IMS shutdown checkpoint command.
Table 25 displays when to issue one of the three IMS shutdown options (FREEZE, DUMPQ, and PURGE) and the effect on the IMS resource.
Recommendation: Cold start the DC component of an IMS subsystem that has been shut down with the LEAVEGR keyword to ensure that all affinities in IMS control blocks are also deleted. The IMS subsystem rejoins the generic resource group during startup.
If the VTAM ACB is closed (usually because of a /STOP DC command), a shutdown checkpoint command with the LEAVEGR keyword is rejected.
If LEAVEPLEX is specified, and the IMS is a member of an IMSplex with global online change enabled, an attempt is made to remove the IMS's ID from the OLCSTAT data set. If there is any error in removing the IMS ID from the OLCSTAT, message, DFS3443, DFS3444, or DFS3448 is written out to the system console and the IMS is shut down. In this case, the IMS ID may still be in the OLCSTAT data set and will have to be deleted using the DFSUOLC utility.
In a shared-queues environment, /CHECKPOINT SNAPQ does not snap the queues because the local IMS subsystem has no local queues. Use the /CQCHKPT command to initiate a CQS structure checkpoint.
In an XRF environment, /CHECKPOINT SNAPQ synchronizes the active and alternate IMS subsystems.
The /CHECKPOINT STATISTICS command does not create a system checkpoint on the log.
Entry ET:
/CHECKPOINT
Response ET:
DFS058I (time stamp) CHECKPOINT COMMAND IN PROGRESS DFS994I *CHKPT 82102/110247**SIMPLE*
Explanation: A simple checkpoint of IMS is written to the system log at 110247 (time) on 82102 (Julian date). The checkpoint number is 82102/110247.
Entry ET:
/CHECKPOINT FREEZE
Response ET:
DFS058I (time stamp) CHECKPOINT COMMAND IN PROGRESS DFS994I *CHKPT 82206/120118**FREEZE*
Explanation: IMS is terminated after all checkpoint freeze functions complete. The checkpoint is written to the system log at 120118 (time) on 82206 (Julian date). The checkpoint number is 82206/120118.
Entry ET:
/CHECKPOINT FREEZE QUIESCE
Response ET:
DFS058I (time stamp) CHECKPOINT COMMAND IN PROGRESS DFS994I *CHKPT 82102/110247**FREEZE*
Explanation: IMS is terminated after all VTAM nodes have returned a shutdown-complete indicator to IMS and IMS has completed all checkpoint freeze functions. The checkpoint is written to the system log at 110247 (time) on 82102 (Julian date). The checkpoint number is 82102/110247.
Entry ET:
/CHECKPOINT PURGE ABDUMP
Response ET:
DFS058I (time stamp) CHECKPOINT COMMAND IN PROGRESS DFS994I *CHKPT 82128/101112**PURGE*
Explanation: IMS is terminated after all checkpoint purge functions complete. The checkpoint is written to the system log at 101112 (time) on 82128 (Julian date). The checkpoint number is 82128/101112.
An z/OS ABEND message is issued when the dump of the IMS control region completes.
Entry ET:
/CHECKPOINT PURGE
Response ET:
DFS058I (time stamp) CHECKPOINT COMMAND IN PROGRESS DFS994I *CHKPT 82103/131415**PURGE*
Explanation: IMS is terminated after all checkpoint purge functions complete. The checkpoint is written to the system log at 131415 (time) on 82103 (Julian date). The checkpoint number is 82103/131415.
Entry ET:
/CHECKPOINT STATISTICS
Response ET:
/DFS058I (timestamp) CHECKPOINT COMMAND IN PROGRESS /DFS994I STATISTICS CHECKPOINT COMMAND COMPLETED
Explanation: IMS performance statistics records are written to the system log. No other information is saved. This checkpoint cannot be used for a system restart.