Adding a chunk to an sbspace

You can add a chunk to an sbspace or temporary sbspace.

About this task

You can specify a metadata area for a chunk, let the database server calculate the metadata area, or use the chunk for user data only.

To add a chunk to an sbspace using onspaces:

Procedure

  1. Ensure that the database server is online, administration, or quiescent mode, or in the cleanup phase of fast-recovery mode.
  2. Use the onspaces -a option to create the sbspace chunk.
    1. Use the -p option to specify the path name, the -o option to specify the offset, and the -s option to specify the chunk size.
    2. If you want to mirror the chunk, use the -m option to specify the mirror path and offset.
    3. To specify the size and offset of the metadata space, use the -Mo and -Ms options.

      The database server allocates the specified amount of metadata area on the new chunk.

    4. To allow the database server to calculate the size of the metadata for the new chunk, omit the -Mo and -Ms options.

      The database server divides the estimated average size of the smart large objects by the size of the user data area.

    5. To use the chunk for user data only, specify the -U option.

      If you use the -U option, the database server does not allocate metadata space in this chunk. Instead, the sbspace uses the metadata area in one of the other chunks.

  3. After you add a chunk to the sbspace, the database server writes the CHRESERV and CHKADJUP log records.
  4. Perform a level-0 backup of the root dbspace and the sbspace.
  5. Use onstat -d and oncheck -pe to monitor the amount of free space in the sbspace chunk.

Example

This example adds a 10-megabyte mirror chunk to sbsp4. An offset of 200 KB for both the primary and mirror chunk is specified. If you are not adding a mirror chunk, you can omit the -m option. The -U option specifies that the new chunk contains user data exclusively.
onspaces -a sbsp4 -p /dev/rawdev1 -o 200 -s 10240 -m /dev/rawdev2 200 -U

You can also define information that Informix® can use to automatically expand the size of a chunk when additional storage space is required for an application. If you have extendable chunks, you are not required to add new chunks or spend time trying to determine which storage space (dbspace, temporary dbspace, sbspace, temporary sbspace, or blobspace) will run out of space and when it will run out of space.

When the CHUNK_OVERLAP_PROTECTION configuration parameter is enabled, the database server ensures that the new chunk does not overlap with other chunks. If the server finds that chunks overlap, the addition of the new chunk fails.