>>-+-/SWITCH-+--+-SYSTEM--+-------+--+--------+--ACTIVE-+------>< '-/SWI----' | '-FORCE-' '-ABDUMP-' | +-OLDS--+------------+------------------+ | '-CHECKPOINT-' | '-WADS----------------------------------'
>>-+-/SWITCH-+--+-SYSTEM--FORCE--+--------+--+--------+-+------>< '-/SWI----' | '-ABDUMP-' '-BACKUP-' | +-OLDS--+------------+------------------+ | '-CHECKPOINT-' | '-WADS----------------------------------'
Table 159 lists the environments (DB/DC, DBCTL, and DCCTL) from which the command and keywords can be issued.
Command / Keywords | DB/DC | DBCTL | DCCTL |
---|---|---|---|
/SWITCH | X | X | X |
ABDUMP | X | X | |
ACTIVE | X | X | |
BACKUP | X | X | |
CHECKPOINT | X | X | X |
FORCE | X | X | |
OLDS | X | X | X |
SYSTEM | X | X | |
WADS | X | X | X |
The /SWITCH command is used to switch active data sets or change between the active and alternate systems. Certain combinations of keywords are valid only in the active or alternate systems, as shown in the format in the syntax diagram. For a list of the commands recovered, see Commands Recovered During Emergency Restart.
/SWITCH SYSTEM without the FORCE keyword causes the active system to attempt to gracefully quiesce before the alternate system becomes active. System activity currently in progress is allowed to complete. New activity is queued. This disables surveillance on the active system, but not the alternate. Therefore, surveillance (if enabled) will eventually trigger a takeover if it does not eventually quiesce.
Unless the optional FORCE keyword is specified, the command is only operable when entered on the active system.
This command is rejected if no unused WADS is available, or for dual logging, if no unused pair of WADS is available.
Entry ET:
/SWITCH OLDS
Response ET:
DFS3257I ONLINE LOG NOW SWITCHED DFS058I 17:10:51 SWITCH COMMAND COMPLETED
Entry ET:
/SWITCH OLDS CHECKPOINT
Response ET:
DFS3257I ONLINE LOG NOW SWITCHED - FROM DFSOLP01 TO DFSOLP02 DFS058I 17:12:53 SWITCH COMMAND COMPLETED DFS2719I MSDB CHECKPOINT WRITTEN TO MSDBCP2 DFS994I *CHKPT 91057/171254**SIMPLE* DFS3499I ACTIVE DDNAMES: MODBLKSA IMSACBA FORMATA MODSTAT ID: 1 DFS3804I LATEST RESTART CHKPT: 91057/132000, LATEST BUILDQ CHKPT: 91057/132414
Entry ET (Master Terminal for active system IMSA):
/SWITCH SYSTEM FORCE
Response ET:
A response message is not returned for the /SWITCH SYSTEM FORCE command. Any further input to the master terminal of the active system is inhibited.
Response RT (z/OS console for active system IMSA):
The z/OS console for the active system will show a user 0604 abend in progress for IMSA. If the ABDUMP keyword had been included on the /SWITCH command, the 0604 abend would be accompanied by a diagnostic dump of the active system.
Response RT (master terminal for alternate system IMSB):
Figure 6 is a screen that shows some of the messages associated with the beginning of takeover on the alternate system.
02/05/15 15:28:27 RSENAME: DFSRSENM BACKUP TAKEOVER IN PROGRESS IMSB DFS3890I 15:27:18 TAKEOVER REQUESTED DFS970I 15:28:05 UNEXPECTED STATUS ,NODE APPLA ,USER N/A ,SEND ,RC =14,FDB2=13,NSECIT =29,SENSE=00000000,REASON=00 DFS3257I ONLINE LOG CLOSED ON DFSOLP00 DFS3891I 15:28:18 TAKEOVER IN PROGRESS DFS2591I NO MSDB HEADERS FOUND, IMAGE COPY LOAD IGNORED DFS3839I 14:26:46 XRF INITIAL DB PRE-OPEN COMPLETE. DFS3838I 14:28:41 XRF INITIAL DC PRE-OPEN COMPLETE. ------------------------------------------------------------------------- PASSWORD:
Intermediate screens are not shown. They would indicate such takeover functions as:
Figure 7 is a screen that show takeover is complete.
02/05/15 15:30:59 RSENAME: DFSRSENM ACTIVE AWAITING I/O PREVENTION IMSB DFS2716I NO MSDBS FOUND - NO MSDB CHECKPOINT TAKEN DFS994I *CHKPT 85135/152931**SIMPLE** DFS3499I ACTIVE DDNAMES: MODBLKSA IMSACBA FORMATA MODSTAT ID: 11 DFS3804I LAST CHKPT ID VALID FOR RESTART: 85135/152931-BUILDQ: 85135/142629 DFS994I TAKEOVER COMPLETED. DFS3859I 15:29:19 PRIORITY 4 SESSIONS SWITCHED. DFS3860I 15:29:19 ALL TERMINAL SESSIONS SWITCHED. --------------------------------------------------------------------------- PASSWORD:
Takeover is complete and the alternate system is now an active system. The XRF environment status line indicates that the newly created active system is running in I/O toleration mode (awaiting I/O prevention). For a more complete description of I/O toleration and I/O prevention, see the IMS Version 9: Operations Guide.