FairCom ISAM for C

ChangeISAMContext

Change current ISAM context.

Short Name

CHGICON()

Type

ISAM function

Declaration

COUNT ChangeISAMContext(COUNT contextid)

Description

ChangeISAMContext() accepts the context ID returned as the result of a successful call to OpenISAMContext(). If ChangeISAMContext() is successful, the current ISAM position for the data file associated with the context ID is:

Saved in the context ID active just prior to the call to ChangeISAMContext().
Changed to the position stored in the selected context ID.

If the context ID passed to ChangeISAMContext() is the current context for the associated data file, ChangeISAMContext() has no effect.

Return

Value	Symbolic Constant	Explanation
0	NO_ERROR	Successful change.
590	NCON_ERR	Non-existent context ID.

See FairCom DB Error Codes for a complete listing of valid FairCom DB error values.

Example

See the example for OpenISAMContext(). The following example uses ctSetAutoContextId() to increase performance.

FILNO datno1,datno2; /* data file numbers */

pVOID bufptr1,bufptr2; /* data buffer pointer */

COUNT contextID_1,contextID_2,contextID_3; /* context ID's */

OpenFileWithResource(datno1,"data1",ctSHARED);

OpenFileWithResource(datno2,"data2",ctSHARED);

/* move to first record for datno1 using first key */

FirstRecord(datno1 + 1,bufptr1);

/* establish first context for datno1 at first record. keyno == -1 saves all key positions. */

contextID_1 = OpenISAMContext(datno1,-1,-1);

/* move to first record for datno2 using third key. */

FirstRecord(datno2 + 3,bufptr2);

/* establish first context for datno2 at first record. keyno != -1 saves only key value for third key. */

contextID_2 = OpenISAMContext(datno2, datno2 + 3,-1);

NextRecord(datno1 + 1,bufptr1);

/* position datno1 at third record by first key. */

NextRecord(datno1 + 1,bufptr1);

/* Third record by first key becomes the saved position for contextID_1 and contextID_3 becomes the active context for datno1. */

contextID_3 = OpenISAMContext(datno1,-1,-1);

/* move from third record by first key, to the next record using the second key. Call this record 4' */

NextRecord(datno1 + 2,bufptr1);

/* Save record 4' as contextID_3. Make the 3rd record the current position for datno1, and contextID_1 becomes the active context for datno1. contextID_2 is still the active context for datno2. */

ctSetAutoContextId(contextID_1);

/* move to the 4th record by key 1 for datno1.*/

NextRecord(datno1 + 1,bufptr1);