SET modifies certain database characteristics. SET operates on either regions or files.

	Note
	In regions that have journaling enabled and on, you can switch journal files without either requiring standalone access or freezing updates.

Example:

     
     
            MUPIP SET /REGION * /JOURNAL=(ON,NOBEFORE)
     
         

The format of the SET command is:

     
            SE[T] [/qualifier,...] /FILE file-specification | /REGION region-name
     
     
         

The file-specification (or region-list) identifies the target of the SET.

Region-names may be lists and may include the DCL wildcards % and *.

The SET command must include one of the following qualifiers which determine whether the argument to the SET is a file-specification or a region-list

/F[ILE]

Specifies that the argument is a file-specification for a single database file. The /FILE qualifier is incompatible with the /REGION qualifier.

/R[EGION]

Specifies that the argument is a region-list which identifies database file(s) mapped by the current Global Directory. SET /REGION changes multiple files when the parameter contains a list and/or wildcards. The /REGION qualifier is incompatible with the /FILE qualifier.

The optional qualifiers which determine the action(s) for the SET are:

/A[CCESS_METHOD]=BG | MM

Specifies the access method for a GDS database file. This qualifier requires stand-alone database access. For information on ACCESS_METHOD, refer to the "Greystone Database Structure" chapter.

By default, ACCESS_METHOD is established by MUPIP CREATE from information entered in the Global Directory.

/E[XTENSION_COUNT]=integer

Specifies the number of GDS blocks by which an existing database file extends. A file or region name is required. This qualifier requires standalone access. The format of the EXTENSION_COUNT qualifier is:

     
            MUPIP SET /E=INTEGER
     
     
         

/F[LUSH_TIME]=integer

Specifies the amount of time between deferred writes of stale cache buffers. This time is specified as an integer number of delta-time format. This qualifier requires standalone access. The format of the FLUSH_TIME qualifier is:

     
            MUPIP SET /F=TIME
     
     
         

/G[LOBAL_BUFFERS]=integer

Specifies the number of cache buffers for a BG database. This qualifier requires standalone access. For information on determining good working sizes for GLOBAL_BUFFERS, refer to the "Global Directory Editor" chapter.

In general, increasing the number of global buffers improves performance by smoothing the peaks of I/O load on the system. However, increasing the number of global buffers also increases the memory requirements of the system, and a larger number of global buffers can increase the probability of the buffers getting swapped out. If global buffers are swapped out, any performance gain from increasing the number of global buffers will be more than offset by the performance impact of swapping global buffers. Most applications use from 1,000 to 4,000 global buffers for database regions that are heavily used. Fidelity does not recommend using fewer than 256 buffers except under special circumstances.

The minimum is 64 buffers and the maximum is 65536 buffers. By default, MUPIP CREATE establishes GLOBAL_BUFFERS using information entered in the Global Directory.

/L[OCK]_SPACE=integer

Specifies the number of pages allocated to the management of M locks associated with the database. For more information on LOCK_SPACE, refer to the "Global Directory Editor" chapter. A file or region name is required. This qualifier requires standalone access. The format of the LOCK_SPACE qualifier is:

     
            MUPIP SET /L=integer
     
     
         

/[NO]J[OURNAL][=journal-option-list]

Specifies whether the database allows journaling and, if it does, characteristics for the journal file.

/NOJOURNAL specifies that the database does not allow journaling. And also it does not accept an argument assignment.

/JOURNAL specifies journaling is allowed. It takes one or more arguments in a journal-option-list. For a full description of the /JOURNAL qualifier and its keywords, refer the "GT.M Journaling" chapter.

/RES[ERVED_BYTES]=size

Specifies the size to be reserved in each database block. RESERVED_BYTES is generally used to reserve room for compatibility with other implementations of M or to observe communications protocol restrictions. RESERVED_BYTES may also be used as a user-managed fill factor.

The minimum RESERVED_BYTES is 0 bytes. The maximum RESERVED_BYTES is the block size minus the size of the block header which is 7 or 8 depending on your platform. Realistic determinations of this amount should leave room for at least one record of maximum size.