Table E (File architecture)
Holds Large Objects (BLOBs and CLOBs)
Enabled by reorganizing / CREATEing a file with ESIZE greater than 0, and then defining a field with a datatype of CLOB or BLOB (the file must have an ESIZE for the latter to occur).
Available as of Model 204 V7.1
Summary
Storage and manipulation of Large Objects (LOBs) differs greatly depending on whether FILEORG x'100' is set.
Table E Differences Without / With the x'100' Setting
| Function | non x'100' | x'100' |
|---|---|---|
| General space management | LOBs require contiguous space New LOBs are always written starting at EHIGHPG; if ESIZE is reached, Table E is scanned for contiguous space (due to deletes). Table E can 'fill' even with many available pages if the space is fragmented. |
LOBs are stored as a series of chained pages, and new LOBs are written first using those in the reuse queue (due to deletes). Table E will 'fill' only if all pages are used. |
| Storing small amounts of data in a LOB field | Even a single byte of data requires a full page of Table E | File level parameter MINLOBE may be set to permit small (200 bytes or less) of data to be stored directly in the record in Table B. But see the 'Change' section, below. |
| Change a LOB | At the time a LOB is first stored, if you expect to subsequently need to increase its size, you will need to RESERVE the necessary space in the initial add. | LOBs may be changes as needed (on adds and stores, the RESERVE, if present, is ignored). Change statements are not permitted if MINLOBE is in use. (A delete / add or insert may be used). |
| COMPACTE command | Is used to defragment Table E to increase the amount of contiguous space. | The COMPACTE command is not necessary, and attempts to execute it will generate an error. |