setcache

Product	Command type
ClearCase®	cleartool subcommand

Platform
UNIX®
Linux®
Windows®

Description

The setcache command sets MVFS and view cache sizes. Although both dynamic and snapshot views use caches, cache size is more significant for a dynamic view than for a snapshot view.

ClearCase—View caches

The dynamic view caches consist mostly of data retrieved from the VOB and enable the view_server to respond faster to RPCs from client machines. When a view_server process is started, it chooses its cache size from the first of the following sources to yield a value:

The dynamic view's cache size, which is set with mkview –cachesize or setcache –view –cachesize and stored in the file view-storage-dir/.view (on the –cache line)
The view_server host's default cache size, which is set with setcache –view –host and stored as a decimal number in the file /var/adm/rational/clearcase/config/view_cache_size (UNIX and Linux) or ccase-home-dir\var\config\view_cache_size (Windows)
The site-wide cache default, which is set with setcache –view –site or setsite and stored in the site config registry
The default value: 500 KB on 32-bit platforms, 1 MB on 64-bit platforms

Note: If your view uses the host value or the site-wide value and that value is changed, your view's cache size does not change until you invoke setcache –view –default or restart the view_server (with endview –server or a reboot).

The dynamic view cache size is allocated among the individual caches. When specifying a cache size, keep the following guidelines in mind:

The value cannot be smaller than 50 KB for 32-bit platforms or 100 KB for 64-bit platforms.
Do not specify a value larger than the amount of physical memory on the server host that you want to dedicate to this view.
Values greater than approximately 4 MB do not help much in most cases.
Verify your changes by using getcache to check the hit rates and utilization percentages periodically to see whether they have improved.

ClearCase dynamic views—MVFS caches

A host's MVFS caches are used to optimize file system performance:

The directory name cache accelerates name translation. This cache is partitioned into three areas, each of which can be tuned with one of the setcache –mvfs options:
- Directory files (–dirdnc)
- Nondirectory files (–regdnc)
- Names not found (ENOENT) (–noentdnc)
  Note: If processes are actively using the directory name cache, you may see the following error message when trying to resize it:
  
  cleartool: Error: Unable to set some current MVFS parameters to requested values because caches are in active use.
  
  Ask users to stop using ClearCase actively (that is, keep their view contexts, but stop manipulating files) and enter the setcache command again.
The attribute cache accelerates access to file metadata (for example, by the stat and access system calls, which are frequently called during make or clearmake operations). The –vobfreemax and –vobfreemin options establish the high- and low-water marks for the attribute cache for VOB and view-private files that are not currently open; the –mnmax option sets this value for both opened and unopened files.
The cleartext cache accelerates the open system call for files in a VOB and view-private files. The –cvpfreemax and –cvpfreemin options establish the high- and low-water marks for this cache. This cache is never larger than the size of the attribute cache.
The RPC handles cache accelerates RPCs to the dynamic view. The –rpchandles option sets the size of this cache; the value ought to be the maximum simultaneous number of RPCs expected from your host. If this value is too small, the getcache –mvfs command recommends that you adjust its size.

When the MVFS is started, it chooses its cache size from the first of the following sources to yield a value:

Values set by a previous setcache –persistent or setcache –persistent_only.
The default cache size established when ClearCase was installed on the host.
The default value. On the UNIX system and Linux, this is a per-host value based on the size of the host's physical memory. On Windows, the site-wide default is used, regardless of system memory size.

For more information about using setcache, see the discussion of client performance tuning in the IBM Rational ClearCase Administrator's Guide.

Restrictions

Identities

UNIX and Linux:
- For setcache –view, you must be root on the view_server host or the view owner.
- For setcache –view –host and setcache –mvfs –zone, you must be root.
Windows:
- For setcache –view, you must be the view owner.
- For setcache –view –host, you must have create/delete/write permissions on the file ccase-home-dir\var\config\view_cache_size.
- For setcache –mvfs, you must be local administrator or a member of the Administrators group.
For setcache –view –site, you must know the registry password

Locks

No locks apply.

Mastership

(Replicated VOBs) No mastership restrictions.

Options and arguments

Specifying the cache information to change

Default: None.
–vie/w: Sets the cache size for a single view. This immediately changes the cache size; you do not need to kill and restart the view_server.
–vie/w –hos/t: Sets the default cache size for the current host.
–vie/w –sit/e: Sets the site-wide default size for view caches.
–mvfs: Sets cache sizes for the MVFS, either temporarily or persistently.
–zone: Specifies the MVFS cache size for a nonglobal zone on Sun Solaris 10 systems running on SPARC and x86 computers. For more information on using this option, see the administrator help topics. For general information on nonglobal zones, see the Sun Microsystems documentation.

Setting the cache size

Default

None.

–def/ault

With –view, removes the –cache line from the .view file. This immediately sets the size of the view cache to (in priority order) the host size, the site-wide size, or the default size. (SeeDescription.)

With –view –host, deletes the /var/adm/rational/clearcase/config/view_cache_size (UNIX and Linux) or ccase-home-dir\var\config\view_cache_size (Windows) file.

With –view –site, removes the value for the site-wide cache from the registry.

When used with setcache –mvfs, –default must be used with the –persistent or –persistent_only option, and restores MVFS cache values to installed defaults. (See Description.) Setting certain values that force changes in other values may cause setcache to print a message explaining that the new values will not take effect until you restart the MVFS.

–cac/hesize size

Specifies a size for the view_server cache. size must be an integer value of bytes, optionally followed by the letter k to specify kilobytes or m to specify megabytes; for example, 800k or 3m.

Specifying the view

Default: None.
–cvi/ew: Sets the cache size for the current view.
view-tag: Specifies the view for which the cache size is changed.

Specifying the registry password

Default: When you set the sitewide view cache size with –view –site, setcache prompts you for the registry password.
–pas/sword registry-password: Specifies the sitewide registry password.

Specifying MVFS parameters (not applicable to snapshot views)

Default: None. You must specify at least one option. cnt and val must be integer values. For information about default and suggested values, see the IBM Rational ClearCase Administrator's Guide. Setting certain values that force changes in other values may cause setcache to print a message explaining that the new values will not take effect until you restart the MVFS.
–per/sistent: When this option is specified with the options –readdir_blocks or –scalefactor, then the options are set persistently, but are not effective until the MVFS is restarted. In other words, in the contexts of –readdir_blocks or –scalefactor, this option is identical to –persistent_only.
In all other cases, this option specifies that all options are applied immediately and also set persistently. If you do not specify –persistent, options revert to their former values when the MVFS is restarted.
–persistent_only: Specifies that all options will be set persistently but will not take effect until the MVFS is restarted.
–reg/dnc cnt: Sets the number of regular file DNC entries.
–noe/ntdnc cnt: Sets the number of ENOENT (file not found) DNC entries.
–dir/dnc cnt: Sets the number of directory DNC entries.
–vob/freemax cnt: Sets the maximum number of free (unused) attribute cache entries. This is a subset of the total specified by –mnmax.
–cvp/freemax cnt: Sets the number of entries in the cleartext cache.
–rpc/handles cnt: Sets the number of RPC handles cached by the MVFS.
–vobfreemin cnt: Sets the minimum number of mnodes to keep on the VOB free list.
–cvpfreemin cnt: Sets the minimum number of mnodes to keep on the cleartext free list.
–rea/ddir_blocks cnt: Sets the number of blocks cached for each directory read by the MVFS. Valid only with –persistent or –persistent_only.
–mnmax cnt: Sets the initial number of mnodes cached by the MVFS. (Several internal values are derived from this value, but will not be changed until after the MVFS is restarted.)
–sca/lefactor val: Sets the scaling factor used to initialize the MVFS with more memory for better performance. Valid only with –persistent or –persistent_only.
–cto: Enables close-to-open consistency checking.
–ncto: Disables close-to-open consistency checking.
–aca/che: Enables attribute caching.
–nac/ache: Disables attribute caching.
–dnc/ache: Enables directory name caching.
–ndnc/ache: Disables directory name caching.
–rlc/ache: Enables readlink caching.
–nrlc/ache: Disables readlink caching.
–rvc/ache: Enables root version caching.
–nrvc/ache: Disables root version caching.

Examples

The UNIX system and Linux examples in this section are written for use in csh. If you use another shell, you may need to use different quoting and escaping conventions.

The Windows examples that include wildcards or quoting are written for use in cleartool interactive mode. If you use cleartool single-command mode, you may need to change the wildcards and quoting to make your command interpreter process the command appropriately.

In cleartool single-command mode, cmd-context represents the UNIX system and Linux shells or Windows command interpreter prompt, followed by the cleartool command. In cleartool interactive mode, cmd-context represents the interactive cleartool prompt.

Change the cache size for view smg_test.
cmd-context setcache –view –cachesize 800k smg_test
The new view server cache limits are: Lookup cache: 78624 bytes Readdir cache: 327680 bytes File stats cache: 137592 bytes Object cache: 275184 bytes Total cache size: 819200 bytes
Set the site-wide cache size.
cmd-context setcache –view –site –cachesize 2m
Registry password: <enter registry password><ENTER>
...
Set the MVFS scaling factor to 3 (dynamic views).
cmd-context setcache –mvfs –persistent –scalefactor 3