IMS Version 9

Shared Secondary Index Database Commands

The original advantage of a shared index database was that it saved a significant amount of main storage for buffers and some control blocks. However, when VSAM was enhanced with shared resources, the savings in storage became less significant. Now the possible disadvantages of using shared index databases generally outweigh the small amount of space they save.

Commands sometimes operate differently depending on whether they are issued for the first of the secondary indexes or for subsequent secondary indexes. The first secondary index is the first database name specified in the DBDUMP statement of the shared secondary index DBDGEN. This first database is the real database. Other secondary index databases are physically part of the real database but they are logically distinct.

The first column in Table 209 lists the issuing command, the second column lists where the command is issued, the third column lists the affects of the command that was issued, and the fourth column provides additional comments.

Table 209. The Effects of Issuing Shared Secondary Index Database Commands
Issuing the Commands...   On the...   Affects...   Comments

/STOP
/LOCK
First secondary index Only the named database If no applications are scheduled on any shared secondary indexes that cause the authorization of the real database by DBRC, the commands have the same effect as the /DBRECOVERY command on the first secondary index.

When a /DISPLAY command is issued on the shared secondary index database, the subsequent secondary indexes are shown as stopped or locked only if the /STOP, /LOCK, or /DBRECOVERY command was issued.

To undo the /STOP or /LOCK command, issue a /START or /UNLOCK command on the first secondary index.


/STOP
/LOCK
Subsequent secondary indexes Only the named database To undo the /STOP or /LOCK command, issue a /START or /UNLOCK command on the named database.
/DBDUMP First secondary index All databases sharing the secondary index data set The /DBDUMP command quiesces activity on all the indexes in the shared database. The database is then closed and reopened for input only.

To undo the /DBDUMP command, issue a /START command on the first secondary index.

/DBDUMP Subsequent secondary indexes Only the named database The secondary index is available for read only.

To undo the /DBDUMP command, issue a /START command on the named database.

/DBRECOVERY First secondary index All databases sharing the secondary index data set The /DBRECOVERY command quiesces activity on all the indexes in the shared database. The database is then closed and stopped.

When the DISPLAY command is issued on the shared secondary index database, the subsequent secondary indexes are shown as stopped or locked only if the /STOP, /LOCK, or /DBRECOVERY command was issued.

To undo the /DBRECOVERY command, issue a /START command on the first secondary index.

/DBRECOVERY Subsequent secondary indexes Only the named database This command is the same as the /STOP command for the named database. However, the /DBRECOVERY command works immediately, but the /STOP command allows current work to quiesce.

To undo the /DBRECOVERY command, issue a /START command on the named database.

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Copyright: IBM Corporation 1974, 2004 Copyright IBM Corporation 1974, 2004  timestamp Last updated: March, 2004