Starting and stopping database processing
In a data-sharing environment, IMS type-1 commands can act locally, that is, affect the local system only, or can act globally, that is, affect all sharing IMS systems in the sysplex.
The UPDATE command can be routed to individual IMS systems or to all IMS systems in an IMSplex, using an automated operator program like the TSO SPOC.
An IMS command with the LOCAL keyword (or without the GLOBAL keyword) affects only the online IMS system on which you enter it. An IMS command with the GLOBAL keyword first affects the IMS system on which you enter it and then, if it is successful, affects other sharing IMS systems in the sysplex.
When you enter a /START DB or UPDATE DB START(ACCESS) command, either locally or globally, DBRC makes sure that each registered database does not need recovery or backout. The IRLM communicates global commands only in a block-level data-sharing environment.
The following table summarizes the commands that affect data sharing when issued for registered databases. A command entered for a database affects full function transactions; a command entered for an area affects Fast Path transactions.
| Command | Action by DBRC | Effect in local IMS system | Effect in sharing IMS systems |
|---|---|---|---|
| Local | |||
| /RMCHANGE | Can change share level for IMS systems using the database | None | None |
| /START AREA | DATABASE LOCAL or UPDATE | Ensures that the database or area does not need recovery or backout, and records database start | Allows transactions to access the database or area, and can change the access intent if you use the ACCESS= keyword | None |
| Global | |||
| /DBDUMP AREA | DATABASE GLOBAL | Ensures that the database or area does not need recovery or backout, sets a return code for any unauthorized batch IMS systems, records database close, and changes access level to read access | Prevents online updating access | Processes command as if entered locally |
| /DBRECOVERY AREA | DATABASE GLOBAL | Prohibits further authorization | Prevents allocation of database | Processes command as if entered locally |
| /STOP AREA | DATABASE GLOBAL | Records database status as stopped (restricts further authorization) | Stops transactions from accessing the database or area | Processes command as if entered locally |
| /STOP ADS | Records area data set as unavailable | Stops the area data set | Processes command as if entered locally |
| /START AREA | DATABASE GLOBAL | Ensures that the database or area does not need recovery or backout, resets the prohibit-further-authorization and read-only flags, records database start, and can change the access level | Allows transactions to access the database or area | Processes command as if entered locally |
Example: You enter the /START command with the GLOBAL keyword on one IMS system and specify several database names, the IRLM transmits the command to other sharing IMS systems, deleting the names of any databases that are invalid for the local system before it transmits the command, and all sharing IMS systems process the command. In those online data-sharing systems, you see the DFS3334I message followed by the DFS3328I message, which tell you that the global /START command has started and has then completed. The messages include the database names that you include in your command.
If you omit the GLOBAL keyword (or specify the LOCAL keyword), the command applies only to the local online IMS system and does not affect access by any other IMS system.
When you enter a /STOP or UPDATE command locally, no interaction occurs between IMS and DBRC.
Related reading: For the format of these commands in a CICS® environment, see CICS Transaction Server for z/OS® CICS Supplied Transactions.